A:10x-102x=13
B:102x-10x=13
C:102x-13=1x
D:10x+13=102x
如图,爷爷推箱子感到吃力.聪明的芳芳在爷爷推的箱子下面撒一些圆形的沙子后,爷爷感觉轻松多了.这是因为滚动摩擦比滑动摩擦要____ (选填“大”或“小”)得多的缘故.
— were you yesterday?
— I was at school.
图为小强打篮球时的情景,下列说法中正确的是( )