___ I understand what you said about the building of the bridge ,I can't quite agree with you about the building plan.

___ I understand what you said about the building of the bridge ,I can't quite agree with you about the building plan.
A.Before
B.As
C.While
D.Since
A为什么不可以呀？这道题答案选CCCCCCCCCCC
before也可引导分句呀。