Output is now six times _____ it was before liberation.(A) that (B) which (C) what (D) of which并请说明依据,

Output is now six times _____ it was before liberation.(A) that (B) which (C) what (D) of which并请说明依据,
Output is now six times _____ it was before liberation.
(A) that (B) which (C) what (D) of which
并请说明依据,

Output is now six times _____ it was before liberation.(A) that (B) which (C) what (D) of which并请说明依据,
首先排除BD 因为这句话不是定语从句 然后看从句缺少表语 既能引导从句又能在从句中做成分的只能是C

C
what 做后半句中的宾语
个人觉得应该还要在前面加个as,读起来顺一点.