一个加数增加0.02，另一个加数也增加0.02，它们的和是[ ]
A．不变
B．增加0.02
C．增加0.04
答案：C
----Jack hasn’t got a job yet, has he?
---- Oh yes, in fact, he has been ________ for two weeks.
A．after work
B．in work
C．at work
D．out of work
电场强度反映电场的力的特征，电位反映电场的能的特征，电压反映电场力做功的能力。
