there are a large number of chemical factories, the air is likely to be polluted.
A. Where
B. That
C. Though
D. As
网友回答
(答案→)A. Where
B. That
C. Though
D. As
解析：考查状语从句。句意：在有很多化工厂的地方，空气很可能被污染。这里的where在句中做状语，引导的是地点状语从句。That不能引导状语从句，though引导的是让步状语从句。故A正确。