同位语从句求问！求大神解惑！！！

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.

• Anow known to be large prehistoric animals, were usually assumed to be  分析A选项
• Bpresently known as from large prehistoric animals, were usually assumed as  分析B选项
• Cbones now known to be those of large prehistoric animals, were usually assumed to be  分析C选项
• Dbones known at present as of large prehistoric animals, were usually assumed as those of  分析D选项
• Ecurrently known as those of large prehistoric animals, were usually assumed to be those of
  这题bones答案解释说不添加会有就近修饰的嫌疑，想问同位语从句如果不是就近修饰，都要补出修饰物吗？？同位语从句有没说一般是修饰主句主语的说法？？？做逗号动词ing做多了看到修饰都反映成一般直接修饰主句主语了。。。。求解惑。。