Câu hỏi: ............. the experiment three timesnow with different results each time!

A. We’ve done

B. We did

C. We’ve been doing

Câu 1: When I arrived the lecture .............. so I didn’t find it easy to follow.

A. started

B. had started

C. had been starting

Câu 2: The manager interviewed ........... candidates in turn.

A. each of the

B. each

C. every

Câu 3: I finished my essay yesterday but ………. it in to the tutor yet.

A. I’ve given 

B. I haven’t given 

C. I didn’t give

Câu 4: When I arrived the lecture................ soI didn’t find it easy to follow.

A. started

B. had startedcorrect

C. had been starting

Câu 5: If the trend continues, the averageincome ............. by 107% by 2020.

A. will increase

B. will have increased

C. will be increasing

Câu 6: The teacher ............... us how to do theexperiment when the fire bell rang.

A. showed 

B. shown

C. was showing