什么是焦炭塔的冲塔？
参考答案：
冲塔就是指焦炭塔在生焦后期把泡沫层的大量泡沫携带到顶部进入油气线或到分馏塔塔底。
—What do you think of your English teacher?
—I love her. She is really _____ She always has a smile on her face. [ ]
A. outgoing
B. funny
C. friendly
D. serious
关系数据库管理系统应能实现的专门的关系运算包括( )。
A．排序、索引、统计
B．选择、投影、连接
C．关联、更新、排序
D．显示、打印、制表
