A.      now known to be large prehistoric animals, were usually assumed to be

B.       presently known as from large prehistoric animals, were usually assumed as

C.      bones now known to be those of large prehistoric animals, were usually assumed to be

D.      bones known at present as of large prehistoric animals, were usually assumed as those of

E.       currently known as those of large prehistoric animals, were usually assumed to be those of

答案是C,我明白bones now known to be those of large prehistoric animals是any large bones 的同位语。

只是不明白B选项究竟错哪里呢？

不好意思，刚才查了字典

assume 只能是assume that or assume ....to be...

B有两个问题:

1.known的逻辑主语模糊,不如使用同位语bones...清晰;

2.known as后面的成分和前面不平行: N. known as from XX. 

as from 是个固定搭配表示"从什么时候起。。。。"而这里要表达的意思应该是“来自史前大动物的骨头”，而B表示的意思成了“被作为来自史前大动物的骨头而知道”别扭，我觉得as表示“作为”的意思的时候，应该跟名词。直接，作为什么什么的。。。

不过我觉得语法时刻谨记楼上说的“平行”，我的感觉里面考平行的太多太多了，和主谓搭配一样

顶~