关于which的指代，请看看这道题

By
the same techniques used for genetically enhancing plants, making them disease-or-pest resistant, researcher have been able to increase
the amount of protein in potatoes, sweet potatoes, and tobacco.

A By the same techniques used for
genetically enhancing plants, making them

B With the same techniques to genetically
enhance plants, so that they are

C Employing the same techniques used to
genetically enhance plants so that they are

D Employing the same techniques to
genetically enhance plants, which makes them

E Employing the same techniques for
genetically enhancing plants that make them

选d么？这里的which指代的不是句子吧，前面的 Employing the same techniques to
genetically enhance plants，是现在分词做伴随状语吧？？所以说不算指代句子是么？？

谢谢！！

"c中的employing....so that.....伴随状语里面（是做伴随吧？）又套了一个so that，可以么？？?"

我也不太名白.

请会的NN讲讲,

谢谢!!!

1. 现在分词作原因状语吧。我的语法书里没有规定伴随状语一定要放在 句末逗号。

2. which不能指代句子肯定就排除了，which只能指代逗号前的词。

1。谢谢

2。既然是做状语（不是句子阿），为啥不能指代呢？？？