粉尘
参考答案：
系指分散于气体中的细小固体粒子，常由煤、矿石等其它固体物料在机械处理过程中或由风扬起的土壤尘所致。
The number of various educational programs is increasing important roles have been recognized by more and more people.
A．whose
B．where
C．which
D．that
焦油加工的主要任务是获得酚、萘、蒽等纯产品和（）等粗产品。
