2001---1---37

Wampum, beads used as (a form) of exchange (by) some Native Americans, was made of (bits of) seashells, (drill), and strung into belts.

答案是c，可是不知道为什么。而且觉得made,strung两个词使得d看起来更像是有问题，drilled多平行呀。赫赫，说实话，句子看的稀里糊涂，说了笑话，别笑我。

answer:  D    drill------drilled