— Excuse me, what can I do for you?

— Yes. I'd like to place ______ advertisement for ______ used car in your paper.[      ]

A. the; a

B. an; /

C. an; a

D. /; the

下列不是影响酶活性因素的是（）

A.水的用量

B.表面活性剂

C.酸碱度

D.温度