焦油加工的主要任务是获得酚、萘、蒽等纯产品和（）等粗产品。
参考答案：洗油沥青
________, the gathering crowd burst into applause.
A．On entering the hall
B．When he took the floor
C．The speaker took his place
D．No sooner had the speaker entered
草酸钙晶体类型有：（）
A.方晶
B.簇晶
C.针晶
D.砂晶
E.钟乳体
