Directions: For this part, you are allowed thirty minutes to write a composition on the topic Health Gains in Developing Countries. You must base your composition on the following instructions (given in Chinese):
1. 以下图为依据描述发展中国家的期望寿命（life expectancy）和婴儿死亡率（infant mortality）的变化情况。
2. 说明引起变化的各种原因。 范文：
In the developing countries great ..