己内酰胺苯萃取塔为（）塔。
A、填料脉冲
B、筛板萃取
C、转盘萃取
D、脉冲筛板
参考答案：C
I’ve become good friends with several of the students in my school ______ I met in the English speech contest last year.
A．who
B．where
C．when
D．which
常吃“五谷杂粮”有利于身体健康，这是因为 （ ）
A．营养成分单一
B．营养成分全面
C．色香味美
D．④烹饪精良
