题目

 I have always regretted ______ harder at school.     A. not to study                           B. to not study     C. having not studied                     D. not having studied 答案：D下图所示装置有多种用途，下列说法不正确的是      [     ]A．用排空气法收集氢气——气体从装置的b端通入 B．检验二氧化碳气体——瓶内盛放氢氧化钠溶液 C．除去氧气中的水蒸气——瓶内盛放浓硫酸 D．用排水法收集氧气——瓶内先装满水，气体从b端通入