— I don't believe that John can remember what the robber was like.

— You're quite wrong. l know it was dark. but he _____ the robber's face

— I'm sure of it！

A. had seen

B. was seeing

C. did see

D. would see

城市供热管网敷设方式中，最经济的一种敷设方式为( )。

A．无沟敷设

B．不通行地沟

C．通行地沟

D．半通行地沟