---I’m sorry!  I would have taken him to hospital if I had known he was seriously ill.

--- But ______ .

A．you didn't

B．you hadn't

C．he wasn't

D．you aren't

锅炉和省煤器的安全阀的调整，当安装一个安全阀时应按安全阀定压规定中的低值定压。当锅炉上安装两个安全阀时，根据安全阀定压规定，( )。

A．两个均按低值定压

B．两个均按高值定压

C．一个按低值定压，另一个按高值定压

D．两个均既可按低值定压也可按高值定压