GWD-13-Q15

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

我选了B，可是答案是A。这是一个事件对后来的影响，为什么不用完成时态？还有between 1876 and 1904为什么放在of three separate sewer systems 前面？哪位大侠能解答？万分感谢！

顶一下，我也选B了，郁闷，谁来解答下？？