火山灰质硅酸盐水泥不适用于( )工程。

A．有抗渗要求的

B．耐磨性要求较高的

C．处在干燥环境的混凝土

D．有抗硫酸侵蚀要求的一般

E．早期强度要求较高的

Are you still here ? You were here an hour ago . Who ________ for?    [ ]

A. are you waiting        

B. did you wait    

C. were you waiting      

D. do you wait