常考得一种题，请牛人分析分析

Once positioned in space, the Hubble Space Telescope wiil capture light from sources twenty times fainter compared to those that can be decteted by ground based instruments 

A.compared to those that can be decteted

B.compared to those can be decteted

C.than that can be detected

D.than those that can be detected

E.than those dectecing

答案为（D）

A B肯定不对，想问问各位高手，those指代的是什么？看答案应该是指sources。

可是我觉得Hubble Space Telescope 捕获的是 light ，ground based instruments 捕获的也是light，应该是light 和light 进行比较，light显然是单数啊。我觉得此题没有答案，或者应该是than that (that can be) detected。

请各位高手指点一下，先谢谢了啊！

没错，指代sources。主要是说capture light从弱20倍的sources（相比较从地面测得的sources），你仔细想想

比较的是sources

捕捉的都是light，light都是一样的

但Hubble Space Telescope可以捕捉光源弱上20倍的Light,言下之意ground based instruments只能看到sources亮一些的light