看这个题目没有人提问过，我没有电子的题目，不知道谁发发善心帮我吧题目贴上来啊，谢谢了

我的问题是，我当时选d现在看来d的them是不对的，这个没有问题，但是我不明白为什么c里面要用would have,为何不直接用had，是因为前面的might表示这个事情是假想的，是一个假设？那为什么假设的就要用将来时态啊？不明白请指点，谢谢！

152. When the technique known as gene-splicing was invented in the early 1970’s, it was feared that scientists might inadvertently create an “Andromeda strain,” a microbe never before seen on Earth that might escape from the laboratory and it would kill vast numbers of humans who would have no natural defenses against it.

(A) it would kill vast numbers of humans who would have no natural defenses against it

(B) it might kill vast numbers of humans with no natural defenses against it

(C) kill vast numbers of humans who would have no natural defenses against it

(D) kill vast numbers of humans who have no natural defenses against them

(E) kill vast numbers of humans with no natural defenses against them

我想這句句意應該有假設的口氣，"殺死絕大多數可能沒有防禦能力的人"，但話說回來，用had，表示只有過去(1970)年以前是如此?現在就不會這樣了嗎?