Casa ESL · B2 Upper Intermediate · Teacher's Resource
Answer Key Booklet
All 20 units · Steps 1 & 2 · For teacher use only. Do not distribute to students.
Step 1 — Units 1–10
Unit 01
Globalisation & Trade
Exercise 11. had studied / would be working · 2. weren't / would have signed · 3. had invested / would be · 4. didn't rely / wouldn't have hit · 5. had negotiated / would be
Exercise 21. would be living · 2. wouldn't have won · 3. wouldn't be
Reading1. South Korea and Vietnam are cited as countries that experienced rapid industrialisation and rising living standards after embracing open markets. · 2. The author suggests that policymakers should have implemented stronger safety nets alongside trade liberalisation to make the transition less painful.
Unit 02
Ethics & Dilemmas
Exercise 11. wish I hadn't ignored · 2. had acted · 3. wishes she had spoken · 4. had considered · 5. wishes he hadn't trusted
Exercise 21. I wish I had reported the fraud → before it affected so many people. · 2. If only the government had regulated the industry → the environmental damage could have been prevented. · 3. She wishes she had consulted a lawyer → before signing the contract. · 4. If only he had been honest → he wouldn't have lost everyone's trust. · 5. They wish they had invested in safety measures → instead of cutting costs.
Reading1. She hesitated because she risked losing her job and being blacklisted in the industry if she reported the violation. · 2. She regrets not acting sooner. She says, 'If only I hadn't hesitated for so long, the river wouldn't have suffered as much damage.'
Unit 03
Innovation & Disruption
Exercise 11. will have launched · 2. will be testing · 3. will have finished · 4. will be using · 5. will have iterated
Exercise 21. will have invested · 2. will be working · 3. will have replaced
Reading1. The passage predicts that autonomous vehicles will have replaced the majority of human-driven taxis in major cities by 2035. · 2. The author is concerned that regulations will not keep up with technology, meaning companies will have been operating in legal grey areas, and many traditional jobs will have disappeared.
Unit 04
Crime & Justice
Exercise 11. is said that · 2. had / broken into · 3. is believed to have left · 4. had / reviewed · 5. is reported to be
Exercise 21. It is believed that → the defendant acted in self-defence. · 2. She had her passport → confiscated at the border. · 3. The witness is reported to have → changed her testimony under pressure. · 4. He got his conviction → overturned after new evidence emerged. · 5. It is estimated that → white-collar crime costs billions annually.
Reading1. It is estimated that recidivism affects nearly two-thirds of released prisoners within three years. · 2. Scandinavian prisons are designed to resemble normal living environments, and inmates are given access to education, vocational training, and mental health support, prioritising rehabilitation over punishment.
Unit 05
Psychology & Behaviour
Exercise 11. It was / that · 2. What / was · 3. What / is · 4. It is / that · 5. The reason why / is
Exercise 21. It is fear that motivates people to avoid risk. · 2. What surprised the entire research team was the results. · 3. It was peer pressure that made her change.
Reading1. The anchoring effect is a cognitive bias where an initial piece of information disproportionately influences subsequent judgements — for example, an extreme opening offer in a negotiation pulls the final agreement toward that anchor. · 2. Implementing structured decision-making processes such as checklists, second opinions, and deliberate pauses helps counteract automatic thinking patterns.
Unit 06
Architecture & Design
Exercise 11. Completed in 1260 · 2. Having reviewed the environmental report · 3. Overlooking the river · 4. Not knowing the regulations · 5. Damaged by an earthquake
Exercise 21. Built · 2. Having completed · 3. Perched
Reading1. The Bosco Verticale is a pair of residential towers in Milan covered in over 900 trees. Designed by Stefano Boeri, they function as vertical forests that absorb CO2 and produce oxygen, and have inspired similar projects worldwide. · 2. The main challenge is cost — not every developer is willing to invest the additional capital required for sustainable design, despite the long-term savings.
Unit 07
Diplomacy & Negotiation
Exercise 11. has the ambassador faced such a difficult negotiation · 2. did they reject the proposal, but they also imposed new sanctions · 3. had the ink dried on the treaty when protests erupted · 4. should a diplomat make threats · 5. did the talks resume
Exercise 21. Never before had the country → agreed to such significant concessions. · 2. Not only did the sanctions damage the economy, → but they also affected ordinary citizens. · 3. Hardly had the negotiations begun → when the delegation received new instructions. · 4. No sooner had the treaty been signed → than both sides accused each other of violations. · 5. Seldom does a single meeting → resolve a conflict that has lasted decades.
Reading1. Because negotiators had to bridge the gap between developed and developing nations and find acceptable language for countries with vastly different economic realities, with new issues constantly emerging. · 2. Critics note that some signatories began retreating from their commitments almost immediately after signing, which exposes the fragile nature of diplomatic consensus.
Unit 08
Sustainability & Climate
Exercise 11. Despite · 2. Nevertheless · 3. Whereas · 4. Although · 5. however
Exercise 21. Despite · 2. whereas · 3. However
Reading1. Despite overwhelming scientific consensus and decades of international agreements, global carbon emissions continue to rise and fossil fuels still dominate the energy supply. · 2. Experts argue that a fundamental shift in consumption patterns, energy policy, and international cooperation is needed — technological progress alone will not be sufficient.
Unit 09
Identity & Culture
Exercise 11. The fact that / is · 2. What / was · 3. Whether · 4. that · 5. What / is
Exercise 21. The fact that she speaks four languages → reflects her multicultural upbringing. · 2. What concerns many linguists → is the rate at which languages are dying. · 3. Whether or not full assimilation is achievable → depends on many social and personal factors. · 4. It is widely recognised that → stereotypes can cause real psychological harm. · 5. What makes a culture resilient → is its ability to adapt while preserving core values.
Reading1. Research shows that people who maintain a connection to their heritage culture while engaging with their new environment tend to have stronger psychological well-being. · 2. The challenge is to create spaces where multiple identities are not merely tolerated but genuinely valued.
Unit 10
Artificial Intelligence
Exercise 11. could replace · 2. appear to be · 3. It could be argued that · 4. tends to · 5. would appear to be
Exercise 21. suggests · 2. Arguably · 3. tends to
Reading1. Arguably, the most pressing concern is the lack of transparency in how AI systems reach their decisions — affected individuals may have no way of understanding why a decision was made. · 2. The passage compares it to concerns about industrialisation, noting that the technology itself is neither good nor bad — it is the way it is deployed that determines its impact on society.
Step 2 — Units 11–20
Unit 11
Philosophy & Thought
Exercise 11. attend · 2. be · 3. were · 4. seek · 5. have
Exercise 21. resign · 2. were · 3. remain · 4. be · 5. were
Reading1. Determinists believe that every action is the inevitable result of prior causes such as genetics, upbringing, and environment. · 2. Compatibilism proposes that free will does not require the absence of causation, only the absence of coercion, thereby reconciling determinism with moral responsibility.
Unit 12
Migration & Borders
Exercise 11. over which · 2. which · 3. for which · 4. in which · 5. which
Exercise 21. The region from which → they originated has been devastated by conflict. · 2. She learned the local language quickly, → which helped her find employment. · 3. The documents on which → their application depended were lost in transit. · 4. Border controls were relaxed, → which led to a sharp increase in crossings. · 5. The community to which → they belonged organised a welcome event.
Reading1. Maria faced an overcrowded refugee centre, the need to learn a new language, and the difficulty of navigating between her Syrian heritage and her new German identity. · 2. She joined a youth organisation through which she campaigned for better support services for refugees, which eventually led to new local government funding.
Unit 13
Entrepreneurship
Exercise 11. do · 2. did · 3. does · 4. did · 5. does
Exercise 21. She does work hard. · 2. They did succeed. · 3. I do agree, but I have concerns. · 4. He does believe in the project. · 5. We did manage to finish.
Reading1. The company ran out of money because the market was not ready for the product — the idea was ahead of its time. · 2. She bootstrapped the company, iterated rapidly on customer feedback, chose a scalable model, and waited until the market was ready.
Unit 14
Health Systems
Exercise 11. So · 2. Neither · 3. not · 4. so · 5. can
Exercise 21. Neither have I. · 2. So does he. · 3. I'm afraid not. · 4. Neither can I. · 5. I suppose so.
Reading1. The UK provides universal coverage funded through taxation with no charge at the point of care, while the US relies heavily on private insurance. · 2. Both systems were severely tested — hospitals in both countries faced triage crises and neither system proved immune to being overwhelmed.
Unit 15
Digital Privacy
Exercise 11. must have used · 2. can't have known · 3. should have updated · 4. needn't have deleted · 5. must have left
Exercise 21. can't have come · 2. shouldn't have clicked · 3. needn't have bought · 4. must have sold · 5. must have known
Reading1. She discovered that the app must have collected far more data than expected, including her location, contacts, and microphone input, going well beyond what a step-counter would need. · 2. They should have disclosed the breach to users immediately, which they failed to do, resulting in a significant fine from regulators.
Unit 16
Literature & Storytelling
Exercise 11. had been reading · 2. would walk · 3. had been falling · 4. would spend · 5. had been travelling
Exercise 21. She had been waiting at the station for over an hour → when the last train of the evening finally arrived. · 2. Every Sunday without fail, → he would take the same path through the woods. · 3. The wind had been howling since midnight, → and not a single person had slept. · 4. Throughout her childhood, → she would invent elaborate stories for her younger siblings. · 5. He had been working on the manuscript for years → before anyone agreed to publish it.
Reading1. Clara had been living alone and working on a novel about her grandmother's life during the war, though progress had been slow. · 2. The letter changed the direction of both her novel and her understanding of her family — she realised she had been telling the wrong story all along.
Unit 17
Space & Exploration
Exercise 11. is believed to be · 2. is reported to have · 3. Apparently · 4. is thought to · 5. is said to have
Exercise 21. is thought to · 2. Apparently · 3. is believed to have · 4. It seems that · 5. is said to have
Reading1. The planet is reported to have an atmosphere containing water vapour and orbits within the habitable zone of its star, making it a promising candidate for further study. · 2. It seems that organisms on Earth can thrive in extreme conditions — boiling springs, frozen lakes, and even the vacuum of space — suggesting life could exist in environments previously thought impossible.
Unit 18
Gender & Equality
Exercise 11. is · 2. is · 3. is · 4. are · 5. are
Exercise 21. Particularly important is access to education. · 2. Of special concern are the rising dropout rates. · 3. Equally significant is the role of mentorship. · 4. Most striking are the differences between rural and urban areas. · 5. Of particular note is her contribution to the field.
Reading1. The passage highlights progress in women's access to higher education and growing representation in political leadership, with more female heads of state than ever before. · 2. Of special concern are the persistent gender pay gap and the high rates of gender-based violence, along with the need to transform cultural attitudes that lag behind legal reforms.
Unit 19
Democracy & Power
Exercise 11. In the event that · 2. on condition that · 3. Assuming that · 4. provided that · 5. provided that
Exercise 21. provided that · 2. In the event that · 3. on condition that · 4. Assuming that · 5. provided that
Reading1. Democracies can endure provided that institutions remain strong and independent, citizens remain engaged and vigilant, and key safeguards like a free press and fair elections are maintained. · 2. Democratic backsliding occurs when key safeguards are weakened, voter apathy takes hold, corruption goes unchecked, and the government no longer genuinely represents citizens' interests.
Unit 20
The Future of Work
Exercise 11. will be automated next year · 2. It was the new policy · 3. have we seen · 4. necessary that you complete · 5. would resign
Exercise 21. The workplace is being transformed by automation. · 2. Never had I experienced anything like it. · 3. Remote work is what saved many businesses. · 4. It is advisable that you update your skills regularly. · 5. Had the company been able to adapt, it would not have closed.
Reading1. It was the pandemic that accelerated trends like remote work and the growth of the gig economy, making what had been a privilege into a widespread necessity. · 2. The greatest challenge is finding a sustainable balance that protects vulnerable workers from redundancy while embracing innovation, and addressing the growing divide between those who can upskill and those who cannot.