能防止龋齿的微量元素是
A：铁
B：锌
C：镁
D：氟
My mother is a kind and nice woman. ____ One Sunday night, when I was watching the film Harry Potter very happily. Mother asked me to go to bed. ____ that I didn't move. But for a while, I noticed that she didn't say anything. ____ I was so sad that I went into my room and cried. I thought "I have only two nights in a week to enjoy the TV. ____" The next day she cooked and talked with me as usual. I pretended not to hear, but she didn't mind and told me why she didn't allow me to watch TV ____ Then I understood her. I love my mother.
A. But she is very strict with me.
B. Because she wanted me to have a good rest.
C. Then she got angry and turned off the TV.
D. I love the film so much.
E. Why doesn't mother allow me to watch TV?
①实验用的小灯泡的电流约为0.2A，等于____ mA．
②半导体收音机电源的电流约为50mA，等于____ A．
③家用电冰箱的电流约1A，等于____μA．
