请教各位一道题····

saiko13

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

正确答案为A，各位牛牛能告诉我这道题该怎么分析么？

kun861010

extent to好像是固定搭配吧？然后么that 前面不能加介词，light是被动，我是这么理解的。