---There is some doubt _____ the concert will be held as the company intends to redecorate the stadium next week.

---What a pity!

A．where

B．that

C．if

D．how

保温结构由（）组成。

A、保温层、保护层、防水层

B、保护层、防腐层、防水层

C、保温层、保护层、防腐层

D、保温层、防腐层