红红在计算□﹣40÷4时，先算减法，后算除法，结果得到20，正确的结果是（　　）

如图是四种不同生物的细胞结构图，其中含有叶绿体的细胞结构图是（　　）

在△ABC中，∠A=120°，∠B=45°，∠C=15°，则cosB等于（　　）

    Air pollution(污染) is a big problem. It's bad for all 1 things on Earth，and it is not the only one kind of 2.Water pollution makes fishand pollutes our drinking water. Noise pollution makes us get3more easily.

Many countries are making rules(规定) to fight against pollution. They try to stop people 4 burning coal(煤)in the city and releasing(排放) dirty smoke into the5.And if people use 6fewer cars，the air will get 7.

    8earth is our home. We must protect it and not destroy it. That is to say, we should keep the land, water and air 9.At the same time, we had better plant more trees10they can provide a lot of things for us and make our earth beautiful.