15. was / to sit 

16. will visit ( TLD )

17. studies / plays ( HTD - usually - sometimes - S là he - V thêm s/es )

18. doesn't live ( HTD - sự thât/ điều hiên nhiên - S là số ít - does - V nguyên )

19. is watching ( HTTD - hđ xem TV xảy ra ngay lúc đang ns - S là số ít - is - Ving )/ watches ( HTD - often - S là he - V thêm s/es )

20. are ( S chỉ hai ng - số nhiueef - are ) / are cooking ( HTTD - now - S là they - are - Ving )

21. ate ( QKD - last... - V2 )

22. phoned ( QKD - yesterday - V2 )

23. did / go ( QKD - last week - Câu hỏi - Đảo did lên đầu -V sau nguyên )/ satyed / listened ( QKD -V2 )

24. am doing ( HTTD - now - S là I - am - Ving )

25. watches ( HTD - often - S là số ít - V thêm s/es )

26. didn't visit ( QKD - last week - câu phủ điịnh - didn't - V sau nguyên )

27. didn't go ( giống câu 26 ) 

28. will have ( TLD - tomorrow )

29. won't come ( TLD - next week )

20. aren't reading ( HTTD - now - S là they - are - Ving )/ are talking ( HTTD ) 

15. We( be ) are tired and we ‘d like (sit) sit down.
16. My parents ( visit ) visit Ha Long Bay this summer vacation.
17. Nam usually ( study ) studiesin the school library in the afternoon , but he sometimes ( play plays soccer with his friends.
18. Mr Minh ( not / live ) don't live in town. His house is in thecountry.
19. My father ( watch ) is watching television in the living-room . He often ( watch ) watches T.V. in the afternoon 
20. Lan and Phuong (be ) are in the kitchen . They ( cook ) are cooking dinner now .
21. We (eat).ate. a delicious dinner at a Mexican restaurant last Wednesday.
22. Yesterday, I (phone).phoned my friend in American.
23. Where did you (go) go.last week? I (stay) stayed.at home and (listen) listened to some English songs on radio.
24. What are you doing now? I (do) am doing my Math exercises.
25. My father often (watch)watchesthe morning news while he is having breakfast.
26. She (not visit) didn't visit her grandmother last week.
27. They (not go) didn't go to school yesterday.
28. We (have) will have Geography tomorrow.
29. He (not come) won't come to see me next weekend.
30.They (not read) aren't reading books now, they (talk) are talking about the film.
           Chúc bạn học tốt. Nhớ vote 5* cho mình nha <3