---Tom, I’m afraid that I can’t catch up with you.

---_____.You are sure to make it.

A．Hurry

B．You’re right

C．Come on

D．You’re welcome

周围物体温度低于人体体表温度时为

A．热辐射
B．正辐射
C．负辐射
D．辐射热
E．辐射源