Usually a meteorological observatory (气象台) air quality in urban areas from one to five: excellent, fairly good, slightly polluted, poor, and dangerous.
A. identifies
B. purifies
C. classifies
D. clarifies
网友回答
A. identifies
B. purifies
(答案→)C. classifies
D. clarifies
解析:考查动词:A. identifies识别,B. purifies使…纯洁,使…净化,C. classifies分类,分别,D. clarifies阐述,说明,句意:通常一个气象观测站把城市中的空气质量分类从一到五:非常好,相当好,轻微污染,差,和危险的。选C。