环氧乙烷精馏塔回流包括（）。
A、塔顶的液相回流
B、塔底的汽相回流
C、塔顶的液相回流与塔底的汽相回流
D、塔顶的液相回流与进料量
参考答案：C
With more and more forests disappearing, today the public is much concerned about the way _________.
A．nature is being ruined
B．which nature is ruined
C．on which to ruin nature
D．of nature to be ruined
专业技术人员对自己专业角色的认同是专业发展的基础和前提。（）
