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

A. Unless

B. had been

C. heavy

D. will

Câu 1: Before went abroad, he had finished his English course at the English-speaking Center.

A. went

B. abroad

C. had finished

D. English-speaking

Câu 2: Ecologists are trying to preserve our environment for future generations by protecting the ozone layer, purifying the air, and have planted the trees that have been cut down.

A. to preserve

B. for

C. the ozone layer

D. have planted

Câu 3: Spell correctly is easy with the aid of a number of word processing programs for personal computers.

A. Spell

B. correctly

C. word processing

D. computers

Câu 4: Please tell us the reason when he left without saying goodbye.

A. tell

B. when

C. left

D. saying

Câu 5: The master of ceremonies announced in a loud and clear voice and told that the dinner would be late due to unforseen circumstances.

A. of ceremonies

B. and told

C. would be

D. due to

Câu 6: Slowly and with care, the museum director removed the Ming vase from the shelf and placed it on the display pedestal.

A. with care

B. from

C. placed

D. the display pedestal