lf the filters become clogged after an unusually short time, send them to the laboratory for analysis of the contamination,如果过滤器在异常短的时间内堵塞，就把它们送到实验室进行污染分析。
A.A lab analysis of the contamination is required to the frequently clogged filters. B.When you find the filters blocked in a very short time, ask the vendor to inspect them for any contamination. C.If the filters get clogged at an unusually early stage, send them to the laboratory to analyze the contamination.正确答案C
