24. Plants have to get enough sunlight. They die.
- If plants don't get enough sunlight , they will die
25. I must finish my essay first. Then I’ll come to the cinema with you.
- If I don't finish my essay , I can come to the cinema with you
26. Mum is still working. We can’t go to the part.
- If mum didn't work , we could go to the park ( park chứ nhỉ ? )
27. David missed the bus this morning. He was late for work.
- If Daved hadn't missed the bus this morning , he would haven't late for work

III. Put the verbs in brackets into the correct tense.
19. A: Why don’t you come out with us tonight?
B: Well, If I ...............finish......................... (finish) my project early, I ............will give......................(give) you a call.
20. A: I can’t believe you’re late again!
B: I’m really sorry. If I ..........didn't get stuck....................... (not / get stuck) in traffic,......................I would be........................ (be) on time.
21. A: Mr Henderson, how do I make pink paint?
B: Well Kim, if you ............mix................... (mix) white and red, you..will get.. (get) pink.
22. A: What should we do, Tommy?
B: I’m not sure. If Dad ............were....... (be) here, he ..............would know..............
. (know) what to do.
23. A: Why didn’t you tell me that Jennifer is back from Rome?
B: Because I didn’t know! If I ................... had seen......................... (see) her, I .....would have told..........
(tell) you!

 Nguyên nhân:  Do không khí có trọng lượng nên Trái Đất và mọi vật trên Trái Đất đều chịu áp suất của lớp không khí bao quanh Trái Đất
 
Hiện Tượng :
Trên nắp bình nước có lỗ nhỏ để áp suất không khí trong bình thông với áp suất khí quyển, đẩy nước xuống.

Gói bim bim phồng to, khi bóc ra bị xẹp............

_{Nguồn : https://hoc24.vn/cau-hoi/the-nao-la-ap-suat-khi-quyen-ap-suat-nay-tac-dung-len-cac-vat-trong-khi-quyen-theo-phuong-nao-neu-vi-du-cho-thay-tac-dung-cua-ap-suat-khi-quyengiup.3410116674430}

1 . X = { 1 , -12 }
2 . X = { 13, -21 }

C / B / C / B / C / A /A /B

A / A / C / A / B /C /A /B /B /C

D / A / D / C / A / A  / B / A

Its eight fifteen
Its six twenty-five
Its three thirty-five