剃刀分为（）和一次性刀刃等。
A.活动刀刃
B.直把刀刃
C.折把刀刃
D.固定刀刃
参考答案：D
对于直线y=3x﹣9，当x( )时，y＜0； 当x( )时，y＞0．
The news on the local radio station，as well as newspaper accounts，confirm that the prison riot was serious.
