①电路中____是电路中形成电流的原因；它是由____提供的．
②电路中形成持续电流的条件是____和____．
③在国际单位制中电压的单位是____．
④一些常见的电压值：一节干电池____；一节蓄电池____；人体的安全电压____；家庭照明电路的电压____．
通读下面的对话，然后根据上下文补全对话内容。A: Good afternoon, Miller! ____ ?B: I'm drawing a horse.A: A horse? Can you let me have a look?B: ____ . Here you are.A: Oh, the horse looks very nice. Do you often draw in your free time?B: ____ .A: Do you like drawing?B: Yes. I like drawing very much.A: ____ ?B: Because it's very interesting. And my art teacher is very kind to me.A: ____ ?B: I have an art lesson once a week.
— ________ is your new bike?
— I ________ about 900 yuan for it.
—Jiff, is it your computer game?
—_____. It's Linda's
