题目

在四棱锥的四个侧面中,直角三角形最多有( )A.1个                   B.2个                   C.3个                   D.4个 答案：思路解析：如图所示的四棱锥S—ABCD中，四边形ABCD是矩形，且SA⊥平面AC，则有SA⊥AB，SA⊥AD，SD⊥DC，SB⊥BC.∴四个侧面均是直角三角形.故选D.答案：D28. After searching through the mountain, they managed to _____ the missing children. A. point               B. place               C. spot          D. site