PREP2的一道语法题

40.        (26538-!-item-!-188;#058&003184)

According to one expert, the cause of genetic irregularities in many breeds of dog is not so much that dogs are being bred for looks or to meet other narrow criteria as that the breeds have relatively few founding members.

(A) the cause of genetic irregularities in many breeds of dog is not so much that dogs are being bred for looks or to meet other narrow criteria
            

(B) the cause of genetic irregularities in many breeds of dog is not as much their being bred for looks or meeting other narrow criteria as much

(C) it is not so much the cause of genetic irregularities in many breeds of dog that they are being bred for looks or meeting other narrow criteria as much

(D) it is not so much that the cause of genetic irregularities in many breeds of dog is their being bred for looks or meeting other narrow criteria so much

(E) it is not so much the cause of genetic irregularities in many breeds of dog to be bred for looks or to meet other narrow criteria

答案里面书CDE都是表语从句错误，请问错在哪里了？

查找原来的讨论贴，发现所有的回复都看不到，所以只好重新开贴了，麻烦大家了，谢谢！~

是选A吗？