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 American soldiers ____ Iraq kissed their family goodbye and left in a hurry.
A．got to
B．to be sent to
C．sent to
D．having been sent to
For a firm in perfect competition, as output increases the marginal revenue will most likely:（）
A. increase.
B. decrease.
C. remain constant.
