had the governments and scientists

Question

Had the governments and scientists not worked together，AIDS-related deaths _______ since their highest in 2005．（　　）

A. had not fallen

B. would not fall

C. did not fall

D. would not have fallen

Answer 1

答案：D
根据题干从句中had置于句首可知，此处为虚拟语气中连词if省略情况．由从句中谓语动词had not worked（had done）可知，是对过去情况的假设，所以主句中的谓语动词应用would/could/might/should have done来表示对过去情况的假设．故选D．