将不带电的导体A和带有负电荷的导体B接触后，在导体A中的质子数 （   ）

A．增加

B．减少

C．不变

D．先增加后减少

How are the kids spending their childhood? I can’t help recalling（回忆）that there was a time _______ we played happily and freely in the outside.

A．that

B．which

C．when

D．不填