Vật liệu dưới đây được dùng để chế tạo ruột bút chì

A. Chì

B. Than đá

C. Than chì

D. Than vô định hình

Your car is too dirty! When did you have it___________?

A. to be washed

B. wash 

C. washed 

D. to wash

Mark first________ his wife three years ago when they _________at university.

A. met/ have studied

B. met/ were studying 

C. has met/ studied 

D. met/ had been studying