补充题57

57.   Once positioned in space, the Hubble Space Telescope will capture light from sources twenty times fainter compared to those that can be detected by ground-based instruments. 

 (A) compared to those that can b detected

(B) compared to those they can detect

(C) than that can be detected

(D) than those that can be detected（D）

(E) than those detecting

我选的是C, 我的想法是这道题比较的是light, 为不可数, that修饰单数名词和不可数名词, those 修饰复数名词, 所以用that , 但是答案是D 难到比较的是sources? 

 请教各位,谢谢了