Q15:

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

为什么不能选B?

是不是，介词短语必须放介词之前？

B选项的 to serve 如果放在时间后可能是指代不清吧，另外时间已经发生了，并

且没有延续性，所以用完成时也是不对的，

个人见解而已

现在完成时和一般过去时的区别 :

1. 现在完成时和一般过去时都表示在过去完成的动作, 但现在完成时强调这一动作

与现在的关系, 如对现在产生的结果、影响等，而一般过去时则表示动作发生在过去，

一般不表示和现在的关系。
2.一般过去时常与具体的时间状语连用，而现在完成时通常与模糊的时间状语连用，

或无时间状语。
3.现在完成时表示持续到现在的动作或状态，动词一般是延续性的， 如 live,

teach, learn, work, study, know等

希望能有帮助.而且题目中用一般过去时应该时和具体时间连用吧