A. Whereas in mammals....the tiny tubes ... are arrayed, in birds the tubes form....
whereas 引起对比，主、从句结构对称
B. 冗长、结构不对称
C\ D 用mammals 和 birds' tubes比较，错误
E. Unlike the tiny tubes that convey nutrients to bone cells, which in mammals are arrayed in parallel lines, in birds the tubes
说不清楚，Unlike the tiny tubes that...., which in mammals..., in birds the tubes...比较别扭
不知道这样讲有道理没？ | 
