问一道新东方语法笔记上的题（第一次发帖，请多关照^^)

One automobile manufacturer has announced plans to increase the average fuel efficiency of its sport utility vehicles by 25 percent over the next five years, amounting to roughly five miles per gallon, and representing the first significant change in the fuel efficiency of any class of passenger vehicle in almost two decades.

(A) amounting to rougly five miles per gallon, and representing
(B) amounting to rougly five miles per gallon, and it would represent
(C) an increase that would amount to roughly five miles per gallon and it would represent
(D) an increase that would amount to roughly five miles per gallon and would represent
(E) which is an increase amounting to roughly five miles per gallon, representing

这道题我除了C，E可以排除外，其它有感觉模棱两可，最后选了B。。。。

正确答案是D，我的问题是：AB比较起来各有什么问题，BD比较起来为什么选择了D。

小女子不胜感谢！ ^_^