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
When first_____to the market,these products en-joyed great success. [ ]
A. introducing
B. introduced
C. introduce
D. being introduced
新型头盔采用必性聚碱酸脂注塑成型，分有（）两种。
