A:two times as much
B:twice as many
C:twice as much
D:as twice as much
一架2.5米长的梯子斜靠在一竖直的墙上,这时梯子的顶端距墙脚2.4米。那么梯足离墙脚的距离是( )
已知等腰△ABC的三个顶点都在半径为5的⊙O上,如果底边BC的长为8,那么BC边上的高为 ____.