重点讲解：
1. how are you doing
你好吗；你怎么样；过得怎么样；
eg. How are you doing these days?
这些日子你怎么样？
eg. How are you doing? I can't complain too much.
你好吗？我不能太抱怨。（还不错）。
2. introduce oneself
自我介绍；
eg. Let me introduce myself.
我来自我介绍一下。
eg. he English teacher is asking her students to introduce themselves.
英语老师正在叫她的学生们作自我介绍。
3. a little while
不久，一会儿；
eg. She tried for a little while to live without him but couldn't.
她曾一时试图脱离他独自生活，但发现那是过不下去的。
eg. He won't be back for a little while yet.
他一时半刻还回不来。
