粗苯回收率η=1-а2/а1公式中各符号的意义是什么?
参考答案:
η----表示粗苯回收充
а2----表示洗苯塔后煤气含苯量
а1----表示入洗苯塔(洗苯塔前)煤气含苯量
—Do you think you could successfully light the flame at the opening ceremony?
—_______. This is not the first time for me.
A.Take care
B.Hurry up
C.Not exactly
D.Don’t worry
简述区域产业布局指向的类型。