Choose the right answer: 1. I . when someone knocked at the doord. A. was sleeping B. sleeping C. was...

Certainly! Let's go through each question and find the correct answers:

1. I . when someone knocked at the door.

   • A. was sleeping: This is the correct choice. The past continuous tense ("was sleeping") is used to indicate an ongoing action in the past that was interrupted by another action (someone knocking at the door).

2. After the Sun . , we saw thousands of fireflies.

   • B. had set: The past perfect tense ("had set") is used here to show that the action of the sun setting was completed before we saw the fireflies.

3. When Don arrived we . coffee.

   • C. were having: The past continuous ("were having") indicates that the action of having coffee was ongoing when Don arrived.

4. I’ve been waiting for you . ages!

   • C. for: "For" is used to indicate the duration of time.

5. Cora was reading a letter . Jimmy phoned her.

   • D. when: "When" is used to show that two actions were happening simultaneously, with one interrupting the other.

6. I’ve met him . but I don’t want to see him again.

   • D. before: "Before" indicates that the speaker has already met the person at least once prior to this moment.

7. How long have you been waiting for ?

   • A. the meeting: "The meeting" is the correct object of the waiting action.

8. You failed your exam! It’s such a .

   • A. disappointment: "Disappointment" is the noun form that accurately describes the feeling or situation.

9. His . causes a lot of problems.

   • B. activity: "Activity" is the noun that best fits the context, referring to actions or behaviors that cause problems.

10. You should be at the university, ?

    • A. shouldn’t you: This is a tag question, and it uses the opposite auxiliary verb form to the statement.

11. They will buy a new car, ?

    • C. won’t they: Another tag question, using the negative form of "will."

12. The train . leave in 15 minutes.

    • C. is to: "Is to" is used here to express a scheduled or planned event.

13. You’d better look . your lectures before the exam.

    • B. through: "Look through" means to review or read something quickly.

14. It’s a great chance . a good impression.

    • C. for you to make: This expression indicates an opportunity for someone to do something.

15. I’d rather . tea without sugar.

    • A. drink: "I'd rather" is followed by the base form of the verb, so "drink" is correct.

These answers reflect standard English grammar and usage, providing the most appropriate choices for each question.

1. I was sleeping when someone knocked at the door. The correct answer is A.
2. After the Sun had set, we saw thousands of fireflies. The correct answer is B.
3. When Don arrived we were having coffee. The correct answer is C.
4. I've been waiting for you for ages! The correct answer is C.
5. Cora was reading a letter when Jimmy phoned her. The correct answer is D.
6. I've met him before but I don't want to see him again. The correct answer is D.
7. How long have you been waiting for the meeting? The correct answer is A.
8. You failed your exam! It's such a disappointment. The correct answer is A.
9. His activity causes a lot of problems. The correct answer is B.
10. You should be at the university, shouldn't you? The correct answer is A.
11. They will buy a new car, won't they? The correct answer is C.
12. The train is to leave in 15 minutes. The correct answer is C.
13. You'd better look through your lectures before the exam. The correct answer is B.
14. It's a great chance for you to make a good impression. The correct answer is C.
15. I'd rather drink tea without sugar. The correct answer is A.

1. A. was sleeping
2. C. set
3. C. were having
4. C. for
5. D. when
6. A. yet
7. A. the meeting
8. A. disappointment
9. B. activity
10. A. shouldn,t you
11. C. won,t they
12. C. is to
13. B. through
14. C. for you to make
15. A. drink