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？
