GMATprep-64 请解答一下，谢谢

答案是A。 但不明白为什么C不对，请问：C答案具体有哪些错误呢？

64. Whereas the use of synthetic fertilizers has greatly expanded agricultural productivity in many parts of the world, an increase in their use can create serious environmental problems such as water pollution, and their substitution for more traditional fertilizers may accelerate soil structure deterioration and soil erosion.
A. an increase in their use can create serious environmental problems such as water pollution, and their substitution for more traditional fertilizers
B. an increase in their use can create serious environmental problems like water pollution, and if substituted for more traditional fertilizers, it
C. if these fertilizers are used increasingly, they can create serious environmental problems such as water pollution, and if used as substitutions for more traditional fertilizers, they
D. the increased usage of these fertilizers can create serious environmental problems such as water pollution, while if substituted for more traditional fertilizers, this substitution
E. the increased usage of these fertilizers can create serious environmental problems like water pollution, while their substitution for more traditional fertilizers

whereas连接的部分最好形式对称，A比C优选。而且我觉得这里用名词短语an increase in their use, their subsitution for..来代替if从句更简洁明了。C没有绝对的语法错误，只是从优选的角度排除。至于prep上解释说的substitution 而不是fertilizer本身造成后果，我倒认为不太能成为排除的原因。

我的看法：

and if used as substitutions for more traditional fertilizers, they
they指代什么呢？synthetic fertilizers 还是traditional fertilizers?

原题的句子结构:whereas the ues of....has...,an increase..can..,and substitution...may...

A选项非常之平行对称，都是用动作性名词做主语，情态动词做谓语。连状语从句的主语也是动作性名词the use of.这两天狂做100道PREP发现他们非常喜欢用动作性名词（注意，不是动名词）。

C 选项虽然很对称，但是用两个条件从句改变了原句的意思，原句并没有“如果。。。就有。。发生”的含义。而且像比较A不简洁。

本人非牛，6月初再战，愿与大家多多交流！

D. the increased usage of these fertilizers can create serious environmental problems such as water pollution, while if substituted for more traditional fertilizers, this substitution

那里错误? 请解释一下

本人看法：B——看到有个like——喀嚓

          C——直接以if打头——喀嚓

          D、E——看到有usage——喀嚓

          *理由：至少不符合表达习惯。