— Lend me some more money, will you?

— Sorry, I’ve got ____ at hand myself. You know the MP3 player cost me all I had just now.

A．nothing

B．no

C．none

D．not

辅酶在酶促反应中的作用是（）。

A.启动载体的作用

B.维持酶的空间构象

C.参加活性中心的组成

D.促进中间复合物形成

E.提供必需基团