Electromagnetic radiation is produced by charged particles that are moving
题目
Electromagnetic radiation is produced by charged particles that are moving
A.at the speed of light
B.with zero acceleration
C.with a changing velocity
D.parallel to a fixed magnetic field
答案
变化的电磁场才能产生电磁波.
举一反三
已知函数f（x）=x，g（x）=alnx，a∈R．若曲线y=f（x）与曲线y=g（x）相交，且在交点处有相同的切线，求a的值和该切线方程．
我想写一篇关于奥巴马的演讲的文章,写哪一篇好呢?为什么好
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