Choose the correct verb form for each space. 1. This is the first time I have done/do/did this exam. 2. When I left home this morning it was raining. 3. By the time you arrived at the party, all of the interesting people went/have gone/had gone home! 4. Tomorrow I think it will rain. 5. John didn’t like his job at all and so decided resign/resigning/to resign. 6. I saw your mother while I have walked/was walking/am walking to work. 7. I try/have tried/have been trying to understand this grammar for hours, but I just can’t! 8. Your final exam might/would/can be difficult, but I'm sure you'll pass! 9. I couldn’t come to the party because I did/must do/had to do my homework. 10. You couldn't have/might have/could have chosen a better person for the job. She was perfect! 11. In Britain you mustn't/don't have to/need do military service. 12. We’ve been friends for a long time. We know/knew/have known each other since we were young. 13. If the teachers were/teach/are better, the students would learn more. 14. Why aren't the students told/didn't the students told/weren't the students told that the exam format had been changed? 15. As part of the preparations for this year’s World Cup, a new stadium is being built/is building/will build.

1. This is the first time I have done this exam.
   Правильный вариант: have done.
   После выражения “This is the first time…” обычно используется Present Perfect, потому что речь идёт о первом опыте до настоящего момента.

2. When I left home this morning it was raining.
   Правильный вариант: was raining.
   Past Continuous используется для описания действия, которое происходило в определённый момент в прошлом.

3. By the time you arrived at the party, all of the interesting people had gone home!
   Правильный вариант: had gone.
   Past Perfect показывает действие, которое произошло раньше другого действия в прошлом: сначала люди ушли, потом ты пришёл.

4. Tomorrow I think it will rain.
   Правильный вариант: will rain.
   Для предположения о будущем часто используется Future Simple с will.

5. John didn’t like his job at all and so decided to resign.
   Правильный вариант: to resign.
   После глагола decide используется инфинитив с to: decide to do something.

6. I saw your mother while I was walking to work.
   Правильный вариант: was walking.
   Past Continuous используется для действия, которое происходило в момент другого события в прошлом.

7. I have been trying to understand this grammar for hours, but I just can’t!
   Правильный вариант: have been trying.
   Present Perfect Continuous используется, когда действие началось в прошлом и продолжается до настоящего момента.

8. Your final exam might be difficult, but I'm sure you'll pass!
   Правильный вариант: might.
   Might выражает возможность или вероятность.

9. I couldn’t come to the party because I had to do my homework.
   Правильный вариант: had to do.
   Had to используется, когда говорим о необходимости в прошлом.

10. You couldn’t have chosen a better person for the job. She was perfect!
    Правильный вариант: couldn’t have chosen.
    Эта конструкция означает, что невозможно было сделать лучший выбор.

11. In Britain you don't have to do military service.
    Правильный вариант: don't have to.
    Это означает отсутствие необходимости. Mustn't означало бы запрет.

12. We’ve been friends for a long time. We have known each other since we were young.
    Правильный вариант: have known.
    Present Perfect используется с since, когда действие или состояние началось в прошлом и продолжается сейчас.

13. If the teachers were better, the students would learn more.
    Правильный вариант: were.
    Это Second Conditional: If + Past Simple, would + verb. Говорим о нереальной или маловероятной ситуации в настоящем.

14. Why weren't the students told that the exam format had been changed?
    Правильный вариант: weren't the students told.
    Это Passive Voice в Past Simple: ученикам не сообщили.

15. As part of the preparations for this year’s World Cup, a new stadium is being built.
    Правильный вариант: is being built.
    Present Continuous Passive используется для действия, которое происходит сейчас: стадион строится.

Итоговые ответы:

1. have done

2. was raining

3. had gone

4. will rain

5. to resign

6. was walking

7. have been trying

8. might

9. had to do

10. couldn’t have chosen

11. don’t have to

12. have known

13. were

14. weren’t the students told

15. is being built