37. My friends spent less time playing computer games so as to concentrate on studying for the final exam.

-> so as to: để mà chỉ mục đích 

Dịch: Những bạn học sinh dành ít thời gian vào việc chơi game để tập trung cho việc học vào cuối kì.

38. Linh and Thuong had eaten Quang noodles for breakfast before they went for a walk around Hoi An ancient town.

-> Before + quá khứ đơn ( hành động xảy ra trước : they went for a walk around Hoi An ancient town ) + quá khứ hoàn thành ( hành động xảy ra sau : Linh and Thuong had eaten Quang noodles for breakfast )

39. Many volunteers were very kind to support the victims of the flood in Ha Tinh.

-> S + tobe + adj + to V 

40. If water pollution gets more serious in the future, it will affect the development of the economy and society.

-> If 1: If + S1 + Vs/es, S2 + will + Vinf

37. My friends spent less time playing computer games so as to concentrate on studying for the final exam. [S + V + so as + (not) to + V…]

38. Before going for a walk around Hoi An ancient town, Linh and Thong had eaten Quang noodles for breakfast. (Before + QKĐ, QKHT)

39. Many volunteers were very kind to support the victims of the flood in Ha Tinh.

40. If  water  pollution  gets  more  serious  in  the  future, it  will affect  the  development  of economy and society.

`JK`