Our city has developed into a big city, which is______it used to be.

A．four times larger than that

B．four times the size of what

C．four times the size larger than what

D．as four times the size as that

钢管管件（）厚度均匀、颜色一致、无损坏、流淌。

A、涂层

B、漆膜

C、插口

D、切口