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
“If,” he added at the meeting, “________ enough time, we would certainly have done it better.”
A.given
B.to be given
C.give
D.giving
与程序流程图相比,盒图没有(),因此不允许随意转移控制。