100mL 6mol•L^-1 H₂SO₄ 跟足量锌粉反应，在一定温度下，为了减缓反应进行的速率，但又不影响生成氢气的总量，可向反应物中加入适量的（　　）

A．碳酸钠固体

B．硝酸钠

C．硫酸钾固体

D．醋酸钠固体

根据下列句子的意思及所给的汉语、英语及首字母提示，写出空缺处词语的正确形式。

1. Students should pay attention to l___________ to the teacher in class..

2. Tomorrow is my father's ___________ (四十) birthday.

3. He ran so fast that he ___________ (赶上) the early bus yesterday.

4. She was ___________ (shock) at the news that a volunteer from Hong Kong died in Yushu earthquake.

5. I ___________ (luck) got a chance to be a volunteer for the 2010 World Expo.