[求助]GWD 29 41 我觉得满复杂的句子

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

答案给的A，我实在看不出来后面到底是哪几个成分平行。请大家给指点下。

我觉得是

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.

红色部分是同位语    to be 后面是3个短语的并列

如果是这样的话，第二个不就是to be possibly causing 了吗，这个不是名词了，而是进行时，和其他的不平行啊。

有道理，谢谢。