米氏常数K是一个用来度量（）

A.酶和底物亲和力大小的常数

B.酶促反应速度大小的常数

C.酶被底物饱和程度的常数

D.酶的稳定性常数

E.以上都不是

All the teachers are well aware of the fact that most students, especially teens, need help and encouragement ______ punishment.

A．better than

B．rather not

C．rather than

D．more often