`24` .don't have to 

`=>` don't have to : không cần phải `->` không mang tính bắt buộc cao như mustn't

`25` .had to

`=>` yesterday `->` QKĐ 

`=>` cấu trúc quá khứ đơn : `(+)` S `+` V2/-ed

`=>` have to `+` V-inf : phải làm gì

`26` .`D`.all are correct

`=>` had better `+` V-inf `=` should `+` V-inf `=` ought to `+` V-inf : nên làm điều gì đó

`27` .`A`.mustn't 

`->` it's still a secret : nó vẫn còn là 1 bí mật  `->` cần phải được giữ kín mang tính băt buộc cao 

`->` mustn't `+` V-inf : không được làm điều gì đó 

`28` .`B`.ought not to

`=>` ought not to `+` V-inf : không nên làm điều gì đó

`29` .`B`.must 

`=>` bị động động từ khiếm khuyết : S `+` must/have to/can/might ... `+` be `+` V3/-ed

`30` .`C`.shouldn't

`=>` shouldn't `+` V-inf : không nên làm gì

24. You don't have to be very tall to play football

S + don't + have to + V

25.My car broke down yesterday so I had to catch a taxi to the office.

QK: S + had to + V

26.We should eat as much fruit as possible in order to get as much vitamins for our bodies

S + should + V (nguyên thể)

27.You musn't tell anyone what I've revealed to you. It's still a secret.

S + musn't + V (inf)

28.If you still want to maintain this relationship, you musn't behave improperly like that.

S + musn't + V (inf)

29.When playing or swimming in the pool, children should be accompanied by thier parents

S + should + V (nguyên thể)

30.We shouldn't go to work by car. Sky train is a wise choice during rush hour

S + shouldn't + V (inf)