催化剂的选择性是指()的能力。
A.加速反应
B.促进主反应
C.保持反应
D.保持再生性能
参考答案:B
—Who would you like to see you off at the airport?
— . A “good-bye” at home is enough.
A. Nobody B. Somebody C. Anybody
掘进机的爬坡能力一般为()。