Traditionally, college students hold a graduation ceremony to encourage themselves before they            on their life jouney.

A．give up

B．settle down

C．get through

D．set off

如果保持冷端温度恒定，热电偶产生热电势的大小（）。

A.只与热端温度有关

B.与热端温度成正比

C.与热端温度成反比

D.将保持不变