再问一道　：）

Gas hydrates, chemical compounds of water and natural gas, are increasingly being studied for their potential to be huge reservoirs of energy, possibly causing sea floor instability, and significant contributors to global warming.

(a)...

(e) as huge reservoirs of energy, as possible causes of sea floor instability, and even as

请问，这里选a不选e的原因？potential to be是固定搭配么？还是因为e中多了even?还是因为cause作动词优于作名词？

answer is e not a

margaret你确定答案是e么？我又查了遍新东方的蓝皮书，给的答案是a阿。。。

so confusing...

yes.i ever did this question,but forget it is from gwd or prep