题目

— Did you go to the party last night? — Yes. And I’d rather ________. It was so________. A．not go; tiresome      B．not have gone; exciting C．not have gone; tiring       D．go; interesting  答案：C 如图，有一块四边形形状的铁皮ABCD，BC＝CD，AB＝2AD，∠ABC＝∠ADB＝90°．(1)求∠C的度数；(2)以C为圆心，CB为半径作圆弧得一扇形CBD，剪下该扇形并用它围成一圆锥的侧面，若已知BC＝a，求该圆锥的底面半径；(3)在剩下的材料中，能否剪下一块整圆做该圆锥的底面？并说明理由．