先化简，再求值：（$\frac{x}{x+y}$﹣$\frac{x^2}{x^2+2xy+y^2}$）÷（$\frac{x}{x+y}$﹣$\frac{x^2}{x^2-y^2}$），其中x=$\sqrt{2}$，y=1．

    I can't help but feel ____(concern) about the ____(destroy) of tropical forests. It is one of the most serious environment problems today. From ____ I know, people are damaging thousands of square ____(kilometer) of forests every day. This is killing hundreds of wild animals that live in the forests.

    ____(fortunate), we do nothing but talk about it. We don't do anything ____(protect) the forests. We need to stop people doing it. There should be ____(strong) laws. I think that people who cut ____ forests should go to prison. That's what should happen to people who destroy the forests and kill wildlife.

    In my opinion, we, human beings, must protect wildlife ____ future generations. Hopefully, our children ____(be) more responsible than we are today.

英国物理学家发现了一条重要的电学定律，通过一段导体的电流跟这段导体两端的电压成正比，跟这段导体的电阻成反比，这位物理学家是____；另一位意大利物理学家托里拆利，首次测量出了大气压强值，一个标准大气压能托起____ cm高的水银柱。

What    she     at the weekend?