38. The river is too dirty we can not swim in.

36. You have to do your homework every day.

37. Nam isn't old enough to drive a car.

39. I used to have a dog last year but I don’t have any more now.

40. It's too dangerous to put a knife into an electrical socket

41. John used to smoke a lot a year ago, but now he doesn’t smoke any more

42. It’s time you went to school

Cấu trúc với Enough to: đủ….để có thể làm gì

Khẳng định

S + V + adv + enough + (for somebody) + to + V

S + to be + adj + enough + (for somebody) + to + V

Phủ định

S + tobe not + adj + enough + (for sb) + to infinitive
S + don’t/doesn’t/didn’t +V + adv + enough + (for sb) + to infinitive

Used to + V1 : đã từng

It's + too + adj + to V : Nó quá làm sao để làm gì

It's time + S + V2/ed : đã đến lúc … phải làm gì

It is (not) necessary = You (not) have to