下列哪项不属于胃酸的生理作用
A.激活胃蛋白酶原
B.使食物中蛋白质变性易于分解
C.杀死进入胃内的细菌
D.促进维生素B12的吸收
参考答案:D
In old Chinese poems, each line has _____ words. [ ]
A. a number of
B. several
C. a good number of
D. a set number of