易形成牙石的个体，洁牙后多少小时又可见到新的牙石（）。
A.12小时
B.36小时
C.24小时
D.48小时
E.60小时
参考答案：D
根据句意，用括号内所给单词的适当形式填空。
小题1:Look at ____________ (you) in the mirror. How dirty your faces are!
小题2:It’s surely the __________ (tough) experience in his life that the brave young man has had.
小题3:Seven ____________ (twelve) of the students in our school are boys.
小题4:All of them want to know how the matter is ____________ (progress) at the moment.
数据流通常采用电脑通信方式进行测量。（）
