问题
选择题
关于电场线，以下说法正确的有：（ ）
A．沿电场线方向，电势一定降低
B．沿电场线方向，场强一定减小
C．电场线在电场中，是客观存在的
D．电场线可以与带电粒子的运动路线重合
答案
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关于电场线，以下说法正确的有：（ ）
A．沿电场线方向，电势一定降低
B．沿电场线方向，场强一定减小
C．电场线在电场中，是客观存在的
D．电场线可以与带电粒子的运动路线重合
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| Hearing is very important to all of us. We can 1 beautiful music, nice songs of birds, the laughter of people or other different kinds of 2 in the world with our ears. 3 we must try to protect our ears. The following will tell you 4 protect ears. Listening to 5 music a lot can be bad for ears, 6 when headphones(耳机) are used. So try not to wear headphones or 7 the volume(音量)when you're wearing headphones. You should give your ears a rest if you like wearing headphones. 8 swimming, remember 9 earplugs (耳塞) into your ears or wear a swim hat to stop water 10 getting into your ears. If you go to a concert, wear earplugs to protect your ears from the terrible music! 11 , special earplugs can be made for you if you go to concerts a lot or if you are a musician yourself. See a 12 if your ears hurt. You'd better 13 as what the doctor says. 14 the suggestions above now and you won't say "What, what… | |||
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