问题 选择题 已知特称命题p:?x∈R,2x+1≤0,则命题p的否定是[ ]A.?x∈R,2x+1>0 B.?x∈R,2x+1>0 C.?x∈R,2x+1≥0 D.?x∈R,2x+1≥0 答案 答案:B