填空题

In the United States, the only pollutant for which there is a national air quality standard is lead.

【参考答案】

NG

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填空题

Low levels of carbon monoxide are not poisonous for healthy individuals.

问答题

1. 表示欢迎2. 介绍学校的有关情况(如图书馆、饭厅和体育活动场所等);3. 遇到困难该如何解决。A Welcome Speech to New Students