目前世界上石油储量最大、生产和输出石油最多的地区是 （     ）

自来水厂常用电解饱和食盐水制备消毒剂Cl₂，反应的化学方程式为：

2NaCl+2H₂O 2NaOH+Cl₂↑+H₂↑．现需要71t氯气用于自来水消毒，理论上需要含杂质10%的粗盐多少吨？

根据括号里所给的汉语写出英语单词。

1.Try to____ （步行)or ride a bike when you travel a short distance.

2.Chinese people usually eat ____  (月饼) on Mid-autumn Day.

3.It isn't ____  (容易的) to learn English well.

4.Do you want to____ (制作) cards by hand for your teachers on Teachers' Day?

5.Cars pollute the ____ (空气)，so remember: Use your legs

A number of children ________ parents had died in the quake were sent to live with families in other cities.