og152-would怎样表达一种comdition呢？

og152-would怎样表达一种comdition呢？  谢谢阿！

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.

it would kill vast numbers of humans who would have no natural defenses against it
it might kill vast numbers of humans with no natural defenses against it
kill vast numbers of humans who would have no natural defenses against it
kill vast numbers of humans who have no natu­ral defenses against them
kill vast numbers of humans with no natural defenses against them

This sentence requires parallel verb forms within the relative clause that might escape... and kill. C, the best choice, uses parallel verb forms that are followed appropriately by the conditional would have in the who clause that modifies humans. Choices A and B each violate parallel construction by intro­ducing a new independent clause, it would kill... and it might kill... Though choices D and E begin by observing parallel­ism, the use of them at the end of each creates a problem of pronoun reference: them cannot refer to the singular microbe. In addition, choices B, D, and E lack would and thus do not express the conditional.