A:a+a2=a3
B:(3a)2=6a2
C:a6÷a2=a3
D:a•a3=a4
①若发现灯L发光,则三个电表中电表示数一定等于零的是____表;
②若有一个电表的示数没有发生变化,则故障可能是____(写出所有可能故障)
This kind of fish is r____ in oil, which is good for people who have heart trouble.