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众所周知，同样的梯子，同样的地面，同样的墙壁，梯子靠墙的角度不同，滑倒的危险也不同。梯子若以不陡的角度搁起来，就有可能出现因梯脚滑移
As we all know, the same ladder, the same ground, the same wall, the different angles of the ladder against the wall, the danger of slipping is also different. Ladders may slip due to a steep angle