2. enable the students to talk about different sources of energy. important point: learning about effect the global warming brings human being. difficult point: to improve the skills of reading. 使用说明及学法指导：1. 通过阅读课本p25-27，完成预习案。2. 完成时间：30分钟。预习案 previewing case task 1 divide the text into 4 parts and match the idea of each part. part 1(para __) two different attitudes among scientists towards global warming. part 2 (para __ to __) whether people should do something about global warming or not.
