乙烯精制系统共脱除()杂质。
A、乙炔
B、CO
C、氧气
D、H2O
E、氯气
参考答案:A, B, C, D
—How are you getting on with your work?
—Oh, I'm sorry. Things aren't going so well as ________.
A.beingplaned
B.planning
C.planned
D.toplan
专业人士可以通过感官检验法分析商品的内在质量,简便易行。