（1）     GWD-30-Q34???????

Books in European libraries last longer than books in libraries in the United States
   because, although the climate in Europe is fairly humid, libraries there are not subjected to the extremes of temperature and humidity that damage collections in the United States. 

1. because, although the climate in Europe is fairly humid, libraries there are not subjected to the extremes of temperature and humidity that

2. because, although the climate in Europe is fairly humid, libraries there are not subject of the extremes of temperature and humidity as those that
3. because, although the climate in Europe is fairly humid, libraries there are not subjected to the extremities of temperature and humidity as
4. because the climate in Europe is fairly humid, but still libraries there are not subject of the extremes of temperature and humidity as
5. because the climate in Europe is fairly humid, but libraries there are not subjected to the extremities of temperature and humidity such as those that

 为甚么选a       because怎么放后面了   不明白

 为甚么选a       because怎么放后面了   不明白

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（1）     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

E

为甚么是e 啊