A:甲对绳的拉力与绳对甲的拉力是一对平衡力
B:甲对绳的拉力与乙对绳的拉力是作用力与反作用力
C:若甲的质量比乙大,则甲能赢得“拔河”比赛的胜利
D:若已对绳的速度比甲快,则已能赢得“拔河”比赛的胜利
______beautiful music she sings!
—Will you please tell us how you can seize the robbers?
—I will spend a whole week ________in your room to wait for their coming.
若一直角三角形的斜边长为c,内切圆半径是r,则内切圆的面积与三角形面积之比是( )