已知△ABC的三个顶点在同一球面上，若∠BAC=90°，AB=AC=2，球心O到平面ABC的距离为1，则该球的半径为 。
桥式抓斗起重机的起升机构应用（）卷筒。
A.标准槽
B.深槽
An analyst estimates that an initial investment of ￡ 500000 in a venture capital project will pay ￡ 6 million at the end of five years if the project succeeds and that the probability the project survives to the end of the fifth year is 25 percent. The required rate of return for the project is 19 percent. The expected net present value of the venture capital investment is closest to:
A．
B．
C．
