—Is it that Jack often plays computer games    makes his parents worry about him ?

—Yes , I think so .               

A．what

B．when

C．that

D．which

流体质点发生相对位移，而引起的热量传递过程，称为（）。

A、传到传热

B、对流传热

C、辐射传热

D、热量迁移