题目

命题“若a≥-1，则x+a≥1nx”的否定是（ ） A. 若a＜-1，则x+a＜1nx       B. 若a≥-1，则x+a＜1nx C. 若a＜-1，则x+a≥1nx       D. 若a≥-1，则x+a≤1nx 答案：B阅读材料 Amy: We have a new classroom. Mike: Let go and have a look Bill: Wow, it's so big. Amy: Let's clean the classroom. Jack: OK, let me clean the blackboard. Mike & Bill: Let’s sweep the floor. Sarah& Amy: Let’s clean the desks. 能力测试选择正确的答案填在括号里。【1】The classroom is ______. （ ）A. big B. small C. nice【2】Jack can clean the _____. （ ）A. window B. floor C. blackboard【3】Bill can clean the _______. （ ）A. window B. floor C. desks