Casa ESL · B1 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
Experiences & Achievements
Exercise 11. have never tried · 2. moved · 3. have already finished · 4. visited · 5. Have / spoken
Exercise 21. have seen · 2. went · 3. has made
Reading1. He has learned to speak three languages. · 2. He climbed Mount Fuji in 2021 with his brother.
Unit 02
Future Plans & Ambitions
Exercise 11. am going to learn · 2. will help · 3. is having · 4. will be · 5. are going to move
Exercise 21. I'll answer the phone. → spontaneous decision · 2. We're flying to Rome on Tuesday. → fixed arrangement · 3. She's going to take the exam in June. → pre-decided plan · 4. I think robots will do most jobs in the future. → prediction based on opinion · 5. Look — the bus is going to leave without us! → prediction based on evidence
Reading1. She is going to finish her master's degree in June. · 2. Because the sector is growing quickly.
Unit 03
Storytelling
Exercise 11. was reading / rang · 2. were driving / started · 3. was cooking / cut · 4. were playing / began · 5. was listening / didn't hear
Exercise 21. was waiting / noticed · 2. were watching / went · 3. was walking / bumped
Reading1. The writer was reading a novel when the train stopped. · 2. She was a journalist from Buenos Aires who was writing a book about European railways.
Unit 04
Giving Advice
Exercise 11. should see · 2. had better leave · 3. shouldn't spend · 4. ought to review · 5. had better not ignore
Exercise 21. I have a job interview tomorrow. → You should prepare some answers to common questions. · 2. I've been feeling very tired lately. → You ought to go to bed earlier. · 3. The deadline is in one hour and I haven't started. → You'd better start immediately. · 4. I want to improve my English. → You should practise speaking every day. · 5. My landlord said he'll change the locks if I don't pay. → You'd better pay the rent today.
Reading1. The writer feels exhausted, can't sleep well, has stopped exercising, and argues with their partner. · 2. She advises the writer ought to talk to their manager about their workload.
Unit 05
Describing Processes
Exercise 11. is grown · 2. were built · 3. are delivered · 4. was written · 5. are given
Exercise 21. was reviewed · 2. are produced · 3. was broken
Reading1. They are harvested from trees in tropical regions such as West Africa and South America. · 2. They are crushed and the shells are removed.
Unit 06
Making Comparisons
Exercise 11. as / as · 2. more / better · 3. far more expensive · 4. as big as · 5. the best
Exercise 21. The longer you wait, → the harder it becomes. · 2. This phone is not as fast → as the latest model. · 3. The film was far more interesting → than I thought it would be. · 4. Her presentation was just as good → as his — maybe even better. · 5. The more coffee I drink, → the less I sleep at night.
Reading1. Cities are more convenient, and shops, hospitals, and public transport are much more accessible. · 2. The countryside is not as polluted as urban centres.
Unit 07
Expressing Opinions
Exercise 11. Although · 2. However · 3. On the other hand · 4. Nevertheless · 5. Furthermore
Exercise 21. In my opinion · 2. Nevertheless · 3. However
Reading1. The writer believes everyone deserves access to higher education regardless of their financial situation. · 2. Critics argue that free education would be extremely costly for taxpayers.
Unit 08
Health & Wellbeing
Exercise 11. don't sleep / will feel · 2. will lose / exercises · 3. rains / will cancel · 4. won't improve / practise · 5. takes / will recover
Exercise 21. If you drink enough water, → you will have more energy during the day. · 2. If she doesn't see a doctor, → her condition might get worse. · 3. Unless you reduce your stress, → you won't sleep well at night. · 4. If people walk more, → air pollution in cities will decrease. · 5. If you skip breakfast every day, → you will often feel tired by mid-morning.
Reading1. You will reduce your risk of heart disease by up to twenty per cent. · 2. Unless you take care of your mental health, physical improvements alone won't be enough.
Unit 09
Technology & Communication
Exercise 11. had / would start · 2. would travel / didn't have · 3. didn't use / would have · 4. would / do / were · 5. were / would be
Exercise 21. were / would buy · 2. rains / will stay · 3. knew / would tell
Reading1. They would probably still use paper maps to find their way around cities. · 2. Some studies suggest we would feel less anxious if we weren't constantly checking notifications.
Unit 10
Environmental Issues
Exercise 11. that · 2. which · 3. whose · 4. where · 5. who
Exercise 21. A drought is a period → that lasts a long time with very little rain. · 2. Greta Thunberg is an activist → who has inspired millions of young people. · 3. The Amazon is a region → where much of the world's biodiversity is found. · 4. A species whose habitat is destroyed → may become endangered or extinct. · 5. Renewable energy is energy → which comes from natural sources like the sun and wind.
Reading1. It was founded by Boyan Slat, a Dutch inventor who was only eighteen years old at the time. · 2. The large floating barriers trap plastic on the ocean surface.
Step 2 — Units 11–20
Unit 11
Travel & Culture
Exercise 11. would · 2. used to · 3. would · 4. used to · 5. would
Exercise 21. used to · 2. would · 3. use to · 4. used to · 5. would
Reading1. The writer used to wake up without a plan and explore whatever city they were in. · 2. The writer used to be quite shy, but the experience made them more open and they learned to appreciate different ways of life.
Unit 12
Work & Career
Exercise 11. enjoyed · 2. would · 3. was · 4. could · 5. didn't
Exercise 21. 'I love this company.' → She said she loved that company. · 2. 'We are planning a team event.' → They said they were planning a team event. · 3. 'I will send the email today.' → He said he would send the email that day. · 4. 'I can work overtime.' → She told her boss she could work overtime. · 5. 'I don't want to relocate.' → He said he didn't want to relocate.
Reading1. She said the company was doing well and that profits had increased by ten percent. · 2. Priya told the manager she wanted to discuss her workload because she said she was feeling overwhelmed.
Unit 13
Education & Learning
Exercise 11. if · 2. where · 3. to · 4. not to · 5. when
Exercise 21. if I had finished the homework · 2. told us to read chapter five · 3. what I was studying · 4. asked me to lend her my notes · 5. if there would be an exam
Reading1. She told them to buy two textbooks and asked them to read the first chapter before the next class. · 2. She asked whether the writer wanted to join a study group and asked them to send her their email address.
Unit 14
Media & News
Exercise 11. much · 2. several · 3. Few · 4. a little · 5. plenty of
Exercise 21. many → countable nouns (e.g., articles, channels) · 2. much → uncountable nouns (e.g., information, news) · 3. a few → countable nouns — small positive amount · 4. a little → uncountable nouns — small positive amount · 5. plenty of → both countable and uncountable nouns
Reading1. Much of the content shared online is not checked by professional journalists, and a lot of it can be misleading. · 2. Experts say we should spend a little time each day reading from reliable outlets and use multiple sources.
Unit 15
Social Issues
Exercise 11. had studied · 2. had known · 3. had received · 4. would have volunteered · 5. had acted
Exercise 21. would have known · 2. would have come · 3. had received · 4. hadn't broken down · 5. had driven
Reading1. Experts said that if the local council had built better flood defences, the damage would not have been so severe. · 2. The organiser said that if more people had volunteered, they would have been able to help everyone sooner.
Unit 16
Art & Entertainment
Exercise 11. painting · 2. to go · 3. living · 4. to help · 5. turning
Exercise 21. enjoy → verb + gerund (-ing) · 2. want → verb + infinitive (to + verb) · 3. avoid → verb + gerund (-ing) · 4. decide → verb + infinitive (to + verb) · 5. suggest → verb + gerund (-ing)
Reading1. The friend suggested going to see a play at the local theatre. · 2. It inspired the writer to consider joining a drama group and to hope to audition for a role next month.
Unit 17
Science & Discovery
Exercise 11. — / the / an · 2. The / the · 3. — / a · 4. the / the · 5. — / the / the
Exercise 21. a · 2. The · 3. — · 4. the · 5. — / —
Reading1. The fish produces its own light, a phenomenon known as bioluminescence. · 2. They believe it could help them understand how life survives in the deepest parts of the ocean.
Unit 18
Relationships & Communication
Exercise 11. turn to · 2. get on with · 3. look forward to · 4. let down · 5. make up
Exercise 21. put up with · 2. brought up · 3. looking forward to · 4. fell out with · 5. let / down
Reading1. Laura felt let down because the writer brought up something personal in front of other people that Laura had told them in confidence. · 2. The writer wrote Laura a long letter to apologise, Laura called the next day, they talked for hours and made up.
Unit 19
Money & Finance
Exercise 11. had · 2. didn't spend · 3. knew · 4. could · 5. didn't have to
Exercise 21. had · 2. were · 3. didn't spend · 4. knew · 5. could
Reading1. The writer wishes they had started saving earlier and had opened a savings account when they got their first job. · 2. Ana has always been careful with money, though she wishes she could be a little more relaxed about spending.
Unit 20
Global Connections
Exercise 11. would speak · 2. weren't · 3. would be · 4. were · 5. cooperated
Exercise 21. If it rains, we stay inside. → Zero conditional · 2. If you study hard, you will pass the exam. → First conditional · 3. If I had more money, I would travel the world. → Second conditional · 4. If they had left earlier, they would have caught the train. → Third conditional · 5. If I had been born in Brazil, I would speak Portuguese now. → Mixed conditional (past → present)
Reading1. We would not communicate the way we do today — people would not be able to collaborate, share ideas, and learn from each other in real time. · 2. Some experts believe that if leaders had taken climate change seriously twenty years ago, we would not face such a crisis now.