【正确答案】 In recent years, it has become a widespread problem that people, especially those who live in cities, don't have enough outdoor exercise. Consequently, more and more people are under subhealth condition and they are apt to fall sick.
The major reasons for people lacking outdoor exercise can be listed as follows. Firstly, the increased competition in modern society forces people to sacrifice their exercise time for hard work. Secondly, the business and housing buildings spring up like mushrooms everywhere; therefore, more and more vacant lands for people to do exercise are occupied.
Considering the seriousness of this problem, effective efforts should be made. Most importantly, people should value health more than work so that they could spare more time for physical training. Furthermore, it is necessary that more parks be opened up for free so that people could have a place to go when they need outdoor exercise.

【答案解析】本文是一篇议论文，话题关于缺乏户外运动的问题，文章内容安排如下：
第一段陈述现象，并简要说明这种现象的危害。
第二段分析人们普遍缺乏户外运动的原因。
第三段提出建议和解决的办法。