镁是一种用途很广的金属，目前世界上60%的镁是从海水（主要含NaCl和MgCl₂等）中提取的．主要步骤如下：

（1）上述步骤中试剂①应过量，理由是____ ．

（2）请写出Mg（OH）₂沉淀与试剂②发生中和反应的化学方程式____　．

（3）无水MgCl₂在熔融状态下通电得到金属镁和物质A，氢气在物质A中燃烧生成物质B，则物质A和B的化学式分别为：A____ 　，B____ ．

刘老师每月的工资是3000元，这里的“3000元”是（  ）

“红军不怕远征难，万水千山只等闲。”当年红军“远征”的直接原因是（    ）

    In the past, most Chinese families have got one child in them. But recently, the government has relaxed the family planning policy, which means each couple are allowed to have two children. Would you like to have a brother or a sister who grows up together with you?

    Now please write a passage of about 80-120 words to introduce your opinion. The following points should be included:

    ⒈Is it necessary for a family to have more than one child? Give at least two reasons for it.

    ⒉What's the situation in your family? Are you the only child or not? List what makes you happy and unhappy.

    ⒊Give at least two suggestions to the families with two children.