尺神经损伤后出现爪状畸形的机制是（）

A.指深屈肌腱的尺侧半由尺神经供应，尺神经损伤后3，4指深屈肌腱功能障碍出现爪状

B.示指及中指不呈爪状是因为支配二指的指深屈肌受正中神经支配

C.主要是因为手内肌的损伤，出现掌指关节过伸，指间关节屈曲所致

D.主要是因为手内肌的损伤，出现掌指关节屈曲，指间关节过伸所致

E.以上说法均不正确

—Do you know about the accident which happened in the center of the city?

—Yes. But it was some time           we realized the truth.

A．before

B．when

C．since

D．until