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下列命题中: ①若p,q为两个命题,则“p且q为真”是“p或q为真”的必要不充分...
下列命题中:
①若p,q为两个命题,则“p且q为真”是“p或q为真”的必要不充分条件.
②若p为:∃×∈R,x2+2x≤0,则¬p为:∀×∈R,x2+2x>0.
③命题“∀x,x2-2x+3>0”的否命题是“∃x,x2-2x+3<0”.
④命题“若¬p,则q”的逆否命题是“若p,则¬q”.
其中正确结论的个数是( )
A.1
B.2
C.3
D.4
考点分析:
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