请教GWD 2的几道语法题，CD上找不到Q16Q20Q29Q30Q33

      请各位赐教，不知道为什么GWD NO.2的题，CD上鲜有讨论，或者是有，因为我这方面比较愚笨，找了很久也找不到。看其他贴上说，“什么TT， GWD独有”。我不太懂什么意思，就不耻下问，一起贴上来了。请各位各抒己见。能解一道是一道。先谢谢了

Q16:

Prospecting for gold during the California gold rush was a relatively easy task, because of erosion, prehistoric glacier movement, and ancient, gold-bearing riverbeds thrust to the surface by volcanic activity put gold literally within reach for anybody with a pan or shovel.

1. because of erosion, prehistoric glacier movement, and ancient, gold-bearing riverbeds thrust to the surface by volcanic activity put gold literally within reach for
2. because of erosion, prehistoric glacier movement, and volcanic activity that thrust ancient, gold-bearing riverbeds to the surface, and putting gold literally within reach of
3. owing to erosion, prehistoric glacier movement, and volcanic activity that had thrust ancient, gold-bearing riverbeds to the surface, and putting gold literally within reach of
4. since erosion, prehistoric glacier movement, and volcanic activity that thrust ancient, gold-bearing riverbeds to the surface, putting gold literally within reach for

5. since erosion, prehistoric glacier movement, and ancient, gold-bearing riverbeds thrust to the surface by volcanic activity put gold literally within reach of

请问为什么不是D呢？我觉得activity与erosion ,movement语意上更加平行而不是riberbeds，

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Q20:
                

Sulfur dioxide, a major contributor to acid rain, is an especially serious pollutant because it diminishes the respiratory system’s ability to deal with all other pollutants.

1. an especially serious pollutant because it diminishes the respiratory system’s ability to deal
2. an especially serious pollutant because of diminishing the respiratory system’s capability of dealing

3. an especially serious pollutant because it diminishes the capability of the respiratory system in dealing

4. a specially serious pollutant because it diminishes the capability of  the respiratory system to deal
5. a specially serious pollutant because of diminishing the respiratory system’s ability to deal

 请问为什么不是C？我的理由是A of B  优于 A'B

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Q29:

Several financial officers of the company spoke on condition that they not be named in the press reports.

1. that they not be named

2. that their names will not be used
3. that their names are not used
4. of not having their names
5. of not naming them

请问：为什么是C？是因为公司的officer  spoke后面所以要用一般现在时？

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Q30:

Most insomnia is not an illness or a physical condition so much as a symptom of another problem that may simply be a reaction to certain medications, anxiety about travel, or stress before a job interview.

1. an illness or a physical condition so much as a symptom of another problem that may simply be a reaction to certain medications
2. an illness or a physical condition so much as symptomatic of another problem that may be a simple one, like a reaction caused by certain medications
3. so much an illness or a physical condition but a symptom of another problem that may be as simple as when certain medications cause a reaction

4. so much an illness or a physical condition, but it is a symptom of another problem, maybe a simple one like certain medications causing a reaction
5. so much an illness or a physical condition but symptomatic of another problem, maybe simply a reaction to certain medications

请问为什么不是C呢？我觉得not an illness ..not a sumptom更平行.

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Q33:

When an active tooth in the shark’s jaws is lost or worn down, many spare teeth lie in seemingly limitless reserve, each of which are ready to slide into the appropriate position.

1. When an active tooth in the shark’s jaws is lost or worn down, many spare teeth lie in seemingly limitless reserve, each of which are ready to slide into the appropriate position.
2. Whenever an active tooth is lost or worn down, many spare teeth lie in seemingly limitless reserve in the shark’s jaws, which are each ready to slide into the appropriate position.
3. Many spare teeth lie in seemingly limitless reserve in the shark’s jaws, each one of which are ready to slide into the appropriate position when an active tooth is lost or worn down.
4. The many spare teeth lying in seemingly limitless reserve in the shark’s jaws, each one of which is ready to slide into the appropriate position whenever an active tooth is lost or worn down.
5. In the shark’s jaws, many spare teeth lie in seemingly limitless reserve, each one ready to slide into the appropriate position whenever an active tooth is lost or worn down.

请问是因为each one不对，所以不能需选E嘛？A选项 each of which后面为什么用are复数呢？