`34.` David has visited Vietnam twice, so he knows a lots about Vietnamese customs.

`-` HTHT:

S+ has/have + V3/V-ed + O

`-` clause, + so+clause: .. vì vậy ... ( nguyên nhân - kết quả) 

`-` know about sth: biết về cái gì đó 

`35.` You ought not to play video games.

`-` ought  not to do sth: ko nên làm gì đó 

`36.` If you do morning exercise, you will have good health.

`-` Cấu trúc câu điều kiện loại `1`:

If +S+ V(s/es)+O, + S+ will/can/should + V-inf +O.

`37.` Although it rained a lot when we were in Van Ho, we enjoyed our holiday.

`-` Although/Even though/ Though + clause,clause: mặc dù... nhưng ...

34. David has visited Vietnam twice so he knows a lot about Vietnamese customs.

Clause + so + clause: vì vậy

35. You ought not to play video games.

ought not to +V1: không nên làm gì 

36. If you do morning exercise, you will have good health.

If 1: if + HTĐ, S + will/can/shall ..  +V1 

37. Although it rained a lot when we were in VanHo, we enjoyed our holiday.

Although + clause, clause: mặc dù 

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