57. 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 form 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 lifht from a distant galaxy
請問為什麼 denotes the extent 後面一定要加 to which?
還有為什麼一定要用被動語態呢?