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
运营事业总部消防重点单位那些？
It was only after he had read the papers Mr. Gross realized the task Before him was extremely difficult to complete.
A．when
B．that
C．which
D．What
