A、B、C、D四种化合物的焰色反应均为黄色；C、D与盐酸生成一种无色无味气体E，该气体能使澄清石灰水变浑浊；D和A可反应生成C；B和E反应可生成C和另一种无色无味气体F．请回答下列问题：

（1）写出A的电子式：______．

（2）写出B和E反应的化学方程式：______，该反应中氧化剂是______还原剂是______．

（3）写出D和盐酸反应的离子方程式：______．

用所给词的正确形式。

1. When I ________(give) you a present, you must open it at once.

2. American people eat lots of ________ (hamburger) everyday.

3. Can he ________ (help) me ________ (do) the work?

4. It's too difficult ________ (understand)what you are trying ________ (say).

5. He could see the smoke ________ (rise) from the chimney (烟囱) when he

    ________ (walk) past your house at this time yesterday.