求助涛涛GWD-29-41

volleyball

Q41:

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.

 

1. to be huge reservoirs of energy, possibly causing sea floor instability, and
2. to be huge reservoirs of energy, possibly causing sea floor instability, and even as
3. as huge reservoirs of energy, possibly causing sea floor instability, and
4. as huge reservoirs of energy, and the possible cause of sea floor instability,
5. as huge reservoirs of energy, as possible causes of sea floor instability, and even as

答案是A, 我看不出causing 与 contributor 平行对称， 但也找不出完美的答案，

我当时就选了个e。 请哪位给指点一二

谢谢

mbz

here you go:

http://forum.chasedream.com/dispbbs.asp?BoardID=23&ID=178244