Sure, let's go through each question and provide the correct answers along with explanations:

16. By the end of next year, George ___ English for two years.
- A. will have learned
- B. will learn
- C. has learned
- D. would learn

**Answer: A. will have learned**
- **Explanation:** The sentence is referring to a future perfect tense, indicating an action that will be completed by a certain point in the future.

17. Henry ___ into the restaurant when the writer was having dinner.
- A. was going
- B. went
- C. has gone
- D. did go

**Answer: B. went**
- **Explanation:** The past simple tense "went" is used to describe a completed action in the past.

18. He will take the dog out for a walk as soon as he ___ dinner.
- A. finish
- B. finishes
- C. will finish
- D. finishing

**Answer: B. finishes**
- **Explanation:** The present simple tense "finishes" is used in the subordinate clause after "as soon as" to indicate a future action.

19. I ___ from him since he ___ two years ago.
- A. hadn't heard; disappeared
- B. haven't heard; disappeared
- C. didn't hear; has disappeared
- D. will not hear; disappears

**Answer: B. haven't heard; disappeared**
- **Explanation:** The present perfect tense "haven't heard" is used to indicate an action that started in the past and continues to the present. The past simple tense "disappeared" is used for a specific point in the past.

20. After the guests ___, she ___ back into the living-room and ___ off the light.
- A. left; went; turned
- B. had left; had gone; turned
- C. have left; will got; turned
- D. had left; went; turned

**Answer: D. had left; went; turned**
- **Explanation:** The past perfect tense "had left" is used to indicate an action that was completed before another action in the past. The past simple tense "went" and "turned" are used for the subsequent actions.

21. By the time you finish cooking they ___ their homework.
- A. will have finished
- B. will finish
- C. had finished
- D. have finished

**Answer: A. will have finished**
- **Explanation:** The future perfect tense "will have finished" is used to indicate that an action will be completed by a certain future time.

22. I will tell John about it ___.
- A. when I will see him this afternoon.
- B. when I see him this afternoon.
- C. when I saw him this afternoon.
- D. after I had seen him this afternoon.

**Answer: B. when I see him this afternoon.**
- **Explanation:** The present simple tense "see" is used in the subordinate clause after "when" to indicate a future action.

23. I have heard nothing from him since he ___ school.
- A. had left
- B. left
- C. has left
- D. leaves

**Answer: B. left**
- **Explanation:** The past simple tense "left" is used to indicate a specific point in the past.

24. He fell down while he ___ towards the church.
- A. run
- B. runs
- C. was running
- D. had run

**Answer: C. was running**
- **Explanation:** The past continuous tense "was running" is used to indicate an ongoing action in the past.

25. Bill’s mother won’t let him go out with his friends ___.
- A. when he finished his homework
- B. after he had finished his homework
- C. once he finished his homework
- D. until he has finished his homework

**Answer: D. until he has finished his homework**
- **Explanation:** The present perfect tense "has finished" is used to indicate an action that must be completed before another action can occur.

26. Her academic performance has greatly improved since she ___ her study methods.
- A. will change
- B. changed
- C. was changing
- D. would change

**Answer: B. changed**
- **Explanation:** The past simple tense "changed" is used to indicate a specific point in the past.

27. You may not see how important your family is ___.
- A. after you had lived far from home
- B. when you were living far from home
- C. until you live far from home
- D. as soon as you lived far from home

**Answer: C. until you live far from home**
- **Explanation:** The present simple tense "live" is used to indicate a future condition.

28. The city has changed a lot since I last ___ it.
- A. visited
- B. would visit
- C. will visit
- D. visit

**Answer: A. visited**
- **Explanation:** The past simple tense "visited" is used to indicate a specific point in the past.

29. He will take the dog out for a walk ___.
- A. as soon as he finished dinner
- B. as soon as he will finish
- C. as soon as he has finished
- D. as soon as he was finishing

**Answer: C. as soon as he has finished**
- **Explanation:** The present perfect tense "has finished" is used to indicate an action that will be completed before another future action.

30. Ask her to come and see me ___.
- A. when she finished her work
- B. when she has finished her work
- C. after she had finished her work
- D. as soon as she was finishing her work

**Answer: B. when she has finished her work**
- **Explanation:** The present perfect tense "has finished" is used to indicate an action that will be completed before another future action.