题型:填空题 下列命题中______为真命题(把所有真命题的序号都填上).①“A∩B=A”成立的必要条件是“A⊊B”;②“若x2+y2=0,则x,y全为0”的否命题;③“全等三角形是相似三角形”的逆命题;④“圆内接四边形对角互补”的逆否命题. 查看答案
题型:选择题 The man was just about to stand up ____ someone sat on the edge of his overcoat. [ ]A. while B. suddenly C. as D. when 查看答案