On turning on the computer,        .

A．Mum told me to have supper.

B．a game appeared on the screen.

C．there was something wrong with the mouse

D．I found a strange E-mail.

对于一定质量的煤，（）的数值最大。

A.高位发热量

B.低位发热量

C.弹筒发热量

D.恒容发热量