gwd-29-7

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.

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

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

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

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

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

the answer is C,what's wrong with the A-seems more concise

now known to be large prehistoric animals

骨头只能是骨头不能是动物

可是B为什么不对呢？

"assumed as" is wrong

also, "presently known" has no clear referents. 

噢，知道了！！非常感谢！！

第二个bone  跟  第一个bone是一个意思,因为中间有插入语,这样避免歧义