题目

如图，在半径为3的球面上有三点，=90°，,球心O到平面的距离是，则两点的球面距离是   A.                        B.    C.                       D.2 答案：B解析：∵AC是小圆的直径。所以过球心O作小圆的垂线，垂足O’是AC的中点。        O’C＝，AC＝3，∴BC＝3，即BC＝OB＝OC。∴，则两点的球面距离＝ ---What’s wrong with Sally？  ---She was ill. She ______in the rain yesterday.A.caughtB.has caughtC.is caughtD.was caught