下列哪种刷牙方法对清除龈沟附近和邻间隙的菌斑效果最好
A.轻刷法B.水平颤动法C.竖转动法D.重刷法E.横刷法
参考答案:B
After the rich man heard the touching story, he _____ most of his money to charity. [ ]
A. gave in
B. gave off
C. gave away
D. gave out
井眼产生键槽都有哪些原因?怎么处理及预防?