--- How often do you work out?

--- _________, but usually once a week.

A．Have no idea.

B．It depends.

C．As usual.

D．Generally speaking.

关于酶抑制剂的叙述，正确的是

A．使酶变性而降低酶活性

B．都与酶共价不可逆结合

C．都与酶的活性中心内基团结合

D．除去可逆抑制剂后，酶活性可恢复

E．凡能降低酶活性的物质均为酶抑制剂