48. 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 E. being they live
1.代词指代, 数的一致:(一级排除B,E)
2. 词法 : (because句子优选) :(二级排除A,D) A. because 完整的句子 B. on account of / because of n. ==》 此处没有明确的限定名词的内涵 C. Because 》on account of / because of because, which appears in C and E, is preferable here since because can introduce a complete subordinate clause explaining the reason why the golden crab has not been fished extensively . C, which uses because and it as the singular subject of a clause, is the best choice.