请教XDF小蓝上一题

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 galaxy has been shifted

D. of light from a distant galaxy shifting

E.
                of the shift of light from a distant galaxy

请问一下答案为什么选A不选E，to the extent 和extent of 这两个词组都是正确的吧？

后面有了by the rapid motion of the galaxy away from the earth 原句意思为 be shifted by...

XDF好象说 关于Extend的句型有the extend to which 和 to the extend that

而extend of 一般只跟名词 而如果原文用extend of的话就extend of shift of light toward the red 到底是shift toward red还是light toward red意思不清楚了就 

不知道上课的时候你那里是不是这么讲的 呵呵 我就自己理解的说说拉

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