A:18+XY
B:18+XX
C:18+XX或18+YY
D:18+XX或18+XY
—Could you please the radio a bit? It's too loud.
—Sorry, I'll do it right away.
如图,有甲、乙两种地板样式,如果小球分别在上面自由滚动,设小球在甲种地板上最终停留在黑色区域的概率为P1,在乙种地板上最终停留在黑色区域的概率为P2,则( )