关于现代通信和电磁波，下列叙述正确的是（　　）

    We high school students do have some growing pains, but we can get rid of them ____ (correct) and wisely____, some of us are upset____ our body styles and looks. It's unnecessary and it's not important at all. We needn't care about it. It is one's inner beauty ____ matters. Second, we sometimes seem to be misunderstood by our teachers, parents and classmates.____ (face) with this, we can find a proper time to have a heart-to-heart talk with them, trying ____ (remove) the misunderstanding. Some of us have fewer friends. I think being open-minded and friendly will do you good. Third, we may fall behind others____ makes us stressed. Actually we can encourage ____ to work efficiently, full of____ (determine). At last, some of us don't have much pocket money, so we feel unhappy. Isn't it strange? So long as we have some, that's enough. And we can learn ____ to spend money.

在括号里填上适当的整式：

（1）$\frac{3c}{2ab}=\frac{15ac}{\left(\right)}$

（2）$\frac{3xy}{x^2-2x}=\frac{\left(\right)}{x-2}$

（3）$\frac{3ab}{a+b}=\frac{6a^{2}b}{\left(\right)}$．

给出下列函数①$y=x\cos x$②$y={\sin }^{2}x$③$y=\left|x^2-x\right|$④$y=e^x-e^{-x}$，其中是奇函数的是（   ）