7. 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

答案是C, 我挑的是A. 乱选的.可是我看了几遍还是看不出来到底那个更好和选的理由..请那位指点一下. 谢了

我选C      A和B中  now known to be large prehistoric animals可以向前修饰any large bones ，也可以向后修饰谓语动词产生修饰歧义。

C出现名词bones应该为独立主格结构，n+ed/-ing分词形式消灭了前面选项产生的歧义。