5、两人说学校活动(hiking)学生太多，怎么办，S1 BY car，但是有60个人，一次只能带4个人，他要往返多次去接人，费时，他自己也没有办法hiking了;S2，租车(van)，租个Van，足够大，但是贵，每个人得交钱，让这些人交钱会不高兴，能有人就不愿意去了
Key Points:
Problem: The students are going hiking but how they would get there becomes a problem due to the large number of participants.
Solution 1: They can go there by car.
Comment: There are 60 students, while the car can only take four at one time. So the car should run back and forth for several times that the driver may not have a chance of going hiking.
Solution 2: They can rent a van.
Comment: The van is big enough to take everybody at one time, but the expense is so high that everyone has to pay for it. There maybe someone who feels unhappy with this way and cancel his or her plan to go hiking.
6、Biology professor用两种insects解释声音的作用，一种是发出危险信号，比如小的thorn bug遇到危险找妈妈，妈妈收到信号回来保护;另一种是找吃的，tree hopper 找到新鲜叶子会发出信号告诉同伴，一起吃
Key Points:
Point1 : make alarming signals
Eg. Thorn bug
Point 2: find some fresh food
Eg. Tree hopper
