进一退二倍投举例子简介：Cheng Keshu and Su Can were walking side by side on the playground, chatting about things in the school or fun outside the school. Of course, Su Can was talking most of the time and Cheng Keshu was listening.
Cheng Keshu and Su Can were walking side by side on the playground, chatting about things in the school or fun outside the school. Of course, Su Can was talking most of the time and Cheng Keshu was listening.
