`31`. If the air wasn't so dirty, I wouldn't sneeze so much.

`⇒` Cấu trúc: If + S + wasn't/weren't + adj, S + would/wouldn't + Vo.

`32`. The air pollution causes breathing problems.

`⇒` Cấu trúc: N + cause + N

`33`. I have learnt English for 3 years.

`⇒` Cấu trúc: S + have/has + Vpp + for + khoảng thời gian

`34`. English is spoken all over the world.

`⇒` Cấu trúc: S + is/are/am + Vpp + ( by O ) +....

`31.` If the air weren't so dirty, I wouldn't sneeze so much.

Câu điều kiện loại 2: If+S+V2/Ved+..., S+would/could/should/may+Vinf+...

`32.` The air pollution causes breathing problems.

cause+N: gây nên thứ gì đó

`33.` I have learnt English for 3 years.

Cấu trúc thì hiện tại hoàn thành: S+have/has+V3/Ved+...

`34.` English is spoken all over the world.

Câu bị động thì hiện tại đơn: S+am/is/are+V3/Ved+(by O)+...