Câu hỏi: Please tell us the reason when he left without saying goodbye.

A. tell

B. when

C. left

D. saying

Câu 1: When a patient's blood pressure is much higher than it should be, a doctor usually insists that he will not smoke.

A. much

B. than it

C. should be

D. will not

Câu 2: Unless there had been a heavy storm, the climbers will not have died.

A. Unless

B. had been

C. heavy

D. will

Câu 3: Jason’s professor had him to rewrite his thesis many times before allowing him to hand it in.

A. had

B. to rewrite

C. many times

D. allowing

Câu 4: Conservation is the safeguarding and preservation of nature resources.

A. is

B. safeguarding

C. preservation

D. nature

Câu 5: The puppy stood up slowly, wagged its tail, blinking its eyes, and barked.

A. slowly

B. its

C. blinking

D. and

Câu 6: Has the government made a decide to ban the use of chemical weapon yet?

A. has

B. decide

C. to ban

D. use