教学目标：1. To help students discover and learn to use some useful words and expressions
2. To help students discover and learn to use some useful structures
教学内容：
1. The time when I first met Nelson Mandela was a very difficult period of my life.
【导学】（1）period 期间，时期，学校的一节课，周期
Let’s finish this period and have a break.
*a period of rotation 自转周期
