1. So after hearing lee's amazing stories about Botswana, I dropped by t mission offices to drop off another check.

短语注释1：drop by的意思是“顺道拜访，顺便拜访”。例如：

I'll drop by later to check on you. 等一下我会顺道去看看你。

I am just going to drop by the post office . 我要顺路到邮局一下。

短语注释2：drop off是个固定短语，有多个意思。可以表示“不知不觉入睡，打瞌睡，睡着 ”。其英文解释为：If you drop off to sleep, you go to sleep. 例如：

If I do drop off, wake me as soon as Martin arrives, won't you? 如果我确实睡着了，马丁一到就叫醒我好吗?

Just as I was dropping off, a strange thought crossed my mind. 就在我打瞌睡的时候,一个奇怪的念头闪过我的脑海。

Drop off还可以表示“减少，减退”的意思。例如：

The daily toll of casualties has dropped off sharply. 每日伤亡人数已经大大减少。

The recession caused sales to drop off. 经济不景气使销量下降。

Drop off还可以表示“脱落”的意思。例如：

The leaves began to drop off. 树叶开始凋落了。

台词中的意思是基于第三个意思，引申为“撕下，撕扯”的意思。Drop off another check的意思是“私下另外一张支票”。剧情中是指Matt又给了一张支票给Lee去支持非洲贫民。

文法解析：after hearing lee's amazing stories about Botswana是现在分词短语作时间状语。

2. Now they have a pump in their village because of us.

短语注释：because of的意思是“因为，由于”。例如：

She was blacklisted by all the major Hollywood studios because of her political views. 由于她的政见，所有好莱坞大制片公司都拒绝用她。

All flights have been canceled because of bad weather. 因天气恶劣，所有航班均被取消。

3. I could volunteer for the next tour.

词汇注释：volunteer在这里是做动词用，意思是“自愿地或无偿地给予或提供（帮助﹑ 建议等）”。表示自愿参与......，使用其固定搭配模式：volunteer something for something。其中的something可以省略，即：volunteer for something。例如：

I volunteered to act as chauffeur. 我自愿充当汽车司机。

She volunteered （her services） for relief work. 她自愿参加救济工作。