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. to be huge reservoirs of energy, possibly causing sea floor instability, and
B. to be huge reservoirs of energy, possibly causing sea floor instability, and even     as
C. as huge reservoirs of energy, possibly causing sea floor instability, and
D. as huge reservoirs of energy, and the possible cause of sea floor instability,
E. as huge reservoirs of energy, as possible causes of sea floor instability, and          even as

OA is A

to be 和 as 在这里的用法有什么不同？

是不是用上even as 就改变了原来的语气？

答案应该是A

 potential to be huge reservoirs ..., ... causing ..., and ... contributors ...

这个题目关键是要理解逻辑意思，cause的逻辑主语到底是potential还是be reserviors？明

白这个问题后就能明白平行的是to be reservoirs 和 to be contributors