又有新题疑问，关于GWD18套中的几道语法题目。。。求帮忙！

vivian0606

GWD-30-Q20:

Researchers have announced that the magnetic fields emitted by one manufacturer’s security surveillance system, of which type there are 200,000 worldwide, can interfere with pacemakers and that this interaction can bring on missed or irregular heartbeats, nausea, breathlessness, dizziness, and even fainting.

A. of which type there are 200,000 worldwide, can interfere with pacemakers and that

（of which type there are 200,000 worldwide非常别扭，错误形式）

B. of which, worldwide, there are 200,000 of that type, and which can interfere with pacemakers, and

C. of which type there are 200,000 worldwide, they can interfere with pacemakers and

(they指的是researchers还是fields？）

D. 200,000 of which type exist worldwide, interfering with pacemakers, and

（exist是谓语）

E. 200,000 of that type existing worldwide and can interfere with pacemakers, and

（缺少谓语）

答案是D，可是在曼哈顿中看到说，which只能用于非限制性定语从句啊，为什么这里可以这么用？

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.

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

答案是A，但是不明白这里不应该是平行更合适吗？

GWD30-Q29:

Researchers agreed that the study of new treatments for heart attack patients was extremely important but more research was needed to determine that balloon angioplasty preceded with ultrasound was or was not any better for heart attack patients than the balloon procedure by itself.

A. more research was needed to determine that balloon angioplasty preceded with ultrasound was or was not any better for heart attack patients than

B. more research was needed for determining whether or not balloon angioplasty preceded by ultrasound is any better for heart attack patients than is

C. that more research was needed to determine whether balloon angioplasty preceded by ultrasound is any better for heart attack patients than

D. that more research was needed to determine that balloon angioplasty preceded with ultrasound was any better for heart attack patients than

E. that more research was needed for determining that balloon angioplasty preceded by ultrasound is or is not any better for heart attack patients than is，

答案是B，但是我觉得这里用to determine表目的才对，为什么用for？并且是balloon angioplasty with ultrasound 与the balloon procedure 进行比i较，那应该是主语和主语比较，B选项中 than is the balloon procedure by itself 为什么正确？

随Yu而安

最后一题答案是C

vivian0606

没有人可以帮忙回答一下吗。。。自己顶一个