求解CWD18的第15题，谢谢！

小意达de花儿

15: GWD-29-Q7

Until a few centuries ago, any large bones discovered in the fields or caves of Europe, now known to be large prehistoric animals, were usually assumed to be the remains of giants and were often displayed as curiosities in castles, palaces, town halls, churches, and monasteries.

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

正解C，为什么呀

GmatMakeIt

同位语