Directions: The Problem of Human Population
It has been estimated that a thousand years ago there were less than 400 million people on earth. However, in the recent thousand years human population has increased nearly 20 times. Nowadays the world population has reached more than 7000 million. The population explosion has caused many problems. Generally, they come down to four major ones.
First, a lot of people can't get employment, which is a universal problem in the world. Second, in developing countries there are not enough shelters for too many people and so people are not properly housed and even are exposed to the elements. Third, in underdeveloped countries a lot of people suffer from hunger because of food shortage, which in turn causes many other problems, malnutrition, disease, etc. Fourth, there are not enough schools for so many people and so a lot of people are illiterate.
Therefore, to eliminate these problems, human beings should take effective measures to control population.
1. 建造（lay down）更多道路
优点：降低街道拥护程度加速车流（flow of traffic）
How to Solve the Problem of Heavy Traffic
The urban traffic is getting increasingly crowded nowadays in China. The roads are pakced with cars, bicylces and pedestrians and traffic jams, bus delays and traffic accidents are a common scene.
Then how to solve this problem? Some suggest to lay down more roads to make the traffic less crowded and speed up the flow of traffic. Others believe that we should open up more public bus routes, so that more people will take the public buses instead of travelling by cars and bicycles.