一个成年人的牙齿中一般含有（）的水
A、5%
B、10%
C、15%
D、20%
参考答案：B
—_________ are these trousers?
—They are only $15.
A. How many B. How much C. How
甘油明胶中水∶明胶∶甘油的合理配比为
A．20∶20∶60
B．20∶30∶50
C．10∶20∶70
D．10∶30∶60
E．25∶25∶50
