乙烯进料量相同条件下，随着催化剂选择性的提高（）加入量相应降低。
A、氮气
B、甲烷
C、氧气
D、抑制剂
参考答案：C
秦岭——淮河一线的1月份平均气温大约是[ ]
A．8℃
B．0℃
C．－8℃
D．－24℃
The fact that many college graduates get lower pay than some workers has ______ a heated discussion.
A．set out
B．set about
C．set up
D．set off
