GWD 29-Q41,请NN帮分析

xiaoerhei

GWD 29-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

Answer:A

请NN帮分析此句的结构和意思！多谢！

BunnyMayor

here is my two cents:

http://forum.chasedream.com/dispbbs.asp?BoardID=23&ID=176125&replyID=1733029&skin=1