乳酶酸能分解糖类生成乳酸，使
A．胃内酸度升高
B．胃内酸度降低
C．肠内酸度升高
D．肠内酸度降低
E．不改变胃和肠内酸度
参考答案：C
— What do you usually do in your spare time, playing the violin or the piano?
— I do ______ of them. I practice singing with some volunteers. [ ]
A.either
B.both
C.all
D.neither
紧固是指设备各连接部位的紧固。（）
