A:15
B:18
C:19
D:23
如图所示的四个实例中,目的是为了增大摩擦的是( )
把( )种颜色的球各8个放在一个盒子里,至少取出4个球,可以保证取到两个颜色相同的球.
—No , you ________. It is not as serious as the one we went to last week .