OG 10th 57 题 extent后面是不是一定要加句子呢

In astronomy the term "red shift" denotes the extent to which light from a distant galaxy has been shifted toward the red, or long-wave, end of the light spectrum by the rapid motion of the galaxy away from the Earth.

A. to which light from a distant galaxy has been shifted

B. to which light from a distant galaxy has shifted

C. that light from a distant galasy has been shifted

D. of light from a distant galasy shifting

E. of the shift of light from a distant galaxy

我的问题是：

1、为什么一定要用现在完成时？

这里的意思是，【红移】这个术语的意思，一定是现在完成时，必须shift完毕，才能叫红移

2、如果把选项改成：

" to light from a distand galaxy shifted toward....by the rapid motion..."

这样的选项对吗？extent to 后面是不是一定要加句子呢？

这里的to是toward后的介词，定语从句修饰extent，介词前置。

这个选项是错的，没有划线的部分有by，一定是被动，其次没有相应的引导词修饰extent，你的选项错误

另外光本身不会移来移去，一定是某种东西造成的，但是当光做主语的时候，必然用by表被动