you may have, you should gather your courage to face the challenge.

A．However a serious problem

B．What a serious problem

C．However serious a problem

D．What serious a problem

X线管组件散热方式中，效果最好的是（）。

A、密封管套，自然散热

B、密封管套，风扇散热

C、闭路油循环自然散热

D、闭路油循环风冷散热

E、冷水管套内循环散热