A:大于1
B:等于1
C:大于0
D:小于0
图书室的王老师买20本字典花了160元,照这样计算,再买30本还要花____元?
____ ____ ____hiding the fact people will know it sooner or later
如图,O为支点,请画出路灯所受重力G的示意图及其力臂l.