GWD(31) 5- 17,18

Q17:

Concerns about public health led to the construction between 1876 and 1904 of three separate sewer systems to serve metropolitan Boston.

1. Concerns about public health led to the construction between 1876 and 1904 of three separate sewer systems to serve
2. Concerns about public health have led to the construction of three separate sewer systems between 1876 and 1904 to serve
3. Concerns about public health have led between 1876 and 1904 to the construction of three separate sewer systems for serving
4. There were concerns about public health leading to the construction between 1876 and 1904 of three separate sewer systems serving
5. There were concerns leading between 1876 and 1904 to the construction of three separate sewer systems for serving

 我觉得D, E Wordy, to serve 比serving 好,为什么要选A而不能用完成时态B呢?

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Q18:

In California today, Hispanics under the age of eighteen account for more than 43 percent, compared with a decade ago, when it was about 35 percent.

1. In California today, Hispanics under the age of eighteen account for more than 43 percent, compared with a decade ago, when it was about 35 percent.
2. Of the Californians under the age of eighteen, today more than 43 percent of them are Hispanic, compared with a decade ago, when it was about 35 percent.
3. Today, more than 43 percent of Californians under the age of eighteen are Hispanic, compared with about 35 percent a decade ago.
4. Today, compared to a decade ago, Californians who are Hispanics under the age of eighteen account for more than 43 percent, whereas it was about 35 percent.
5. Today, Hispanics under the age of eighteen in California account for more than 43 percent, unlike a decade ago, when it was about 35 percent.

我选的是A, 答案是C

是不是 C 的比较更对等一些?  43% people compared with 35% a decade ago

A虽然用了 people account for 43%, 对照的是 people(省略), 用了when it was about .....就破坏了对称结构?

请教各位高手, 在电脑考试的时候, 发现自己总是有点急噪,  眼睛就不是那么能够一眼看出这些规律了,怎么办

没有人顶?