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【单选题】
下列命题，其中说法错误的是（ ）A.
命题“若x 2 -3x-4=0，则x=4”的逆否命题为“若x≠4，则x 2 -3x-4≠0”
B.
“x=4”是“x 2 -3x-4=0．”的充分条件
C.
命题“若m＞0，则方程x 2 +x-m=0有实根”的逆命题为真命题
D.
命题“若m 2 +n 2 =0，则m=0且n=0”的否命题是“若m 2 +n 2 ≠0，则m≠0或n≠0”
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反馈参考答案：
举一反三
【单选题】How popular was reading aloud in the past?
A.
It was popular only among ancient Greeks and Romans.
B.
It was forbidden, especially in libraries.
C.
It was so popular that writers were all good at it.
D.
It was very popular, and even writers made their manuscripts sound right.
【单选题】患者，女性，15岁，初潮年龄14岁，平素月经周期紊乱，经期长短不一，出血量时多时少，此次月经持续12天，量多。此时，处理上首选（）。
A.
止血
B.
调整周期
C.
促使卵巢恢复功能
D.
促进排卵
E.
减少经量
【简答题】Our company offers a full range of Smart Home products, focusing on your home safer and more convenient, and saving energy. All of the products are , even if what happens behind the scene...
【简答题】As a popular medical treatment in the past, bloodletting usually caused death instead of ______.
【单选题】患者,女性,15岁,初潮年龄14岁,平素月经周期紊乱,经期长短不一,出血量时多时少,此次月经持续12天,量多。此时,处理上首选( )
A.
止血
B.
调整周期
C.
促使卵巢恢复功能
D.
促进排卵
E.
减少经量
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