GWD的一道语法题,, 困惑 which的用法 - ChaseDream

Although improved efficiency in converting harvested trees into wood products may reduce harvest rates, it will stimulate demand by increasing supply and lowering prices, thereby boosting consumption.
A. in converting harvested trees into wood products may reduce harvest
rates, it will stimulate demand by increasing supply and lowering prices,
thereby boosting.
B. In converting harvested trees into wood products may reduce harvest
rates, demand will be stimulated because of increasing supply and
lowering prices, which boost.
C. Of converting harvested trees into wood products may reduce harvest
rates, it will stimulate demand by increasing supply and lowering prices,
which boosts.
D. Of harvested trees being converted into wood products may reduce
harvest rates, it will stimulate demand, because it will increase supply
and lower prices, thereby boosting.
E. When harvested trees are converted into wood products may reduce
harvest rates, demand will be stimulated because of increasing supply
and lowering prices, which boost.

（2）which这里太诡异了，which一般都是就近指代的，前面随便找个名词都可以误认为被which指代，很融资造成奇异的。如果表示前面整句话对后面的影响，也就是最后表结果的话，一般都会出现新名词以概括或者用现在分词。这个是正确答案的两个标志。

我认为it will stimulate demand by increasing supply and lowering prices不对，按理说It只能指代前面的improved efficiency 因为只有这个是单数，这样就变成了efficency通过增加供给和降低价格来刺激需求，而efficency是不可能自己发出这个动作的