Since chromosome damage may be caused by viral infections, medical x-rays, and exposure to sunlight, it is important that the chromosomes of a population to be tested for chemically induced damage be compared with those of a control population. (A) to be tested for chemically induced damage be compared with (B) being tested for damage induced chemically are compared with (C) being tested for chemically induced damage should be compared to (D) being tested for chemically induced damage are to be compared to (E) that is to be tested for chemically induced damage are to be comparable with E用了that is，ETS没有说这个单数有问题，是否A-E的不定式或现分包括E的定语从句都是修饰population的？但是，我觉得这些结构都是应该修饰chromosomes的。 麻烦谁给点建议。谢谢！ | 
