`5`.Because Nam was weak , he couldn't lift the box

`\rightarrow` Because dùng để chỉ nguyên nhân hoặc lý do

`6`.He used to collect stamps anymore

`\rightarrow` S + used to + V : Đã từng

`7`.I haven't seen Nam for three years

`\rightarrow` Thì HTHT : S + have / has + V3 / PII

`\rightarrow` Đặc điểm nhận dạng ; for

`8`.Long is too poor to buy that car

`\rightarrow` Cấu trúc : S + be + too adj + ( for O ) + to V

`\text{@ Fox}`

=>

5. Because Nam was weak, he couldn't lift the box.

-> because S V : bởi vì

6. He used to collect stamps.

-> used to V : đã từng

7. I haven't seen Nam for three years.

-> HTHT, S have/has (not) V3/ed, for + khoảng thời gian

8. Long is too poor to buy that car.

-> too adj to V : quá...đến nỗi không thể