问题
问答题 简答题
粉尘对人体的危害程度和什么因素有关？
答案
参考答案：
决定于粉尘的化学组成及其再空气中的浓度，以及人体接触时间的长短。
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粉尘对人体的危害程度和什么因素有关？
参考答案：
决定于粉尘的化学组成及其再空气中的浓度，以及人体接触时间的长短。
| 任务型阅读。 | ||||||||||||||
is poor. In the poor part, a lot of people never get enough to eat. In the rich part, a lot of people eat too much. In one part, children are hungry and in the other, a lot of people are fatter and fatter and have to go on diets or do some exercise to lose weight. For example, a dog or a cat in North America eats better than a child in the poorer countries. The poor countries have some difficult problems. Sometimes the land is too poor to grow anything on. The land can get better, but people have to do a lot of things first. More experts (专家)should go there to teach people how to enrich their land and how to find water. But rich countries have problems, too. They are not always pleasant places to live in. Sometimes the air is too dirty to breathe (呼吸)and the rivers are too dirty to swim in or to take water. The roads and the streets are full of people and buses. Cars usually move very slowly. Noise is terrible. A lot of people do not have houses to live in. People must do something about these problems. We should do something to make the air and the rivers clean and build more houses. But it will take a long time. |