1 . —What does PM 2. 5 mean？
—It's a professional_____________ indicating the condition of air pollution.
—It's a professional_____________ indicating the condition of air pollution.
| A．number | B．mark |
| C．term | D．item |
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2016-12-12更新
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2卷引用：【区级联考】天津市红桥区2019届高三下学期第二次模拟考试英语试题
