1. The golden crab of the Gulf of Mexico has not been fished commercially in great numbers, primarily on account of living at great depths—2,500 to 3,000 feet down.

(A) on account of living

(B) on account of their living

(C) because it lives

(D) because of living（C）

(E) because they live

请问A为什么不对，B要是改成on account of its living，对吗？谢谢！

D, like A, fails to provide a noun or pronoun to perform the action of living, but even with its the phrases would be more awkward and less clear than it lives.

so, "on account of its living " still not better than it lives.

终于想明白了,OG结实中的idomatic是因为前面有个primarily，是个副词，后面不应该接名词性的成分（我的感觉，单没有理论依据）。

如果没有这个词，我认为because of和on account of都可以