按要求改写句子。

1. People are supposed to shake hands when they meet for the first time. （对画线部分提问）

_______ _______ people supposed to_______ when they meet for the first time?

2. We usually make plans to see friends. (改为同义句 )  

We usually ______ _______ see friends.

3. Someone invited me to go to the restaurant to have dinner.（改为被动语态）  

I ______ _______ to go to the restaurant to have dinner.

4. You should give him something to eat for breakfast.（改为否定句）  

You ______ give him _______ to eat for breakfast．

5. People have pretty relaxing rules in Colombia.（对画线部分提问）

_______ _______ _______ rules do people have in Colombia?

（5分）有一包固体粉末A，可能是NaOH、Na₂SO₄、MgCl₂、CuSO₄中的一种或几种组成，为了分析固体粉末的成分，取少量该固体粉末进行实验，实验方案设计如下：

（1）A中一定含有     ，一定不含     。

（2）若X为“沉淀不溶解”或“沉淀部分溶解”，则A还含有     。若取消实验④，将③中的试剂换为     ，也可得出相同结论。

（3）写出②中化学反应方程式     。