A:电流表坏了或未接好
B:从点a经过灯L1到点b的电路中有断路
C:灯L2的灯丝断了或灯座未接通
D:电流表和灯L1、L2都坏了
Judging from the message they convey, these two chapters are __________ independent of each other, that is, they are not in connection with the other at all.
当y满足____时,|y﹣3|=3﹣y成立.