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【单选题】
第二产程娩出胎儿的重要辅助力量是A.
子宫体收缩力
B.
子宫下段收缩力
C.
腹肌及膈肌收缩力
D.
肛提肌收缩力
E.
圆韧带收缩力
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【单选题】乒乓球是我国人们最爱的运动项目之一,下列关于乒乓球受力及运动的说法中错误的是
A.
击打球的不同部位，球的旋转方向不同，表明力的作用效果与力的大小有关
B.
球在空中飞行时，如果不考虑空气阻力，则乒乓球只受重力作用
C.
球拍击球时，乒乓球和球拍之间的作用力是弹力
D.
运动的乒乓球在碰到桌面后会改变运动方向，表明力可以改变物体的运动状态
【简答题】阅读理解。 John lived in a big city with his wife and his two children. One Sunday afternoon, John took his yellow motorbike (摩托车) out of the room and was washing it when one of his friends came here. The ...
【简答题】Li Qiu is a boy of fif and studying in Grade Three at Oak school. His family lives outside the town. His parents have a farm and grow a lot of vegetables on it and they often sell them in the town...
【简答题】A:根据所给中文及句意，完成下列空格。（7分） The old man ____________ (刷) his dog’s fur every day. 2. Bill is very smart and he can always answer questions ______(正确地). 3. The girl is very young, but she can speak some ...
【简答题】我国的第一个乒乓球世界冠军是谁?
【简答题】遇天气恶劣，信号机显示距离不足200m时，如何办理?
【单选题】乒乓球是我国的国球也是同学们喜爱的运动项目之一。下列说法中正确的是( )
A.
兵乓球被击出后，仍受到球拍的弹力作用
B.
运动的乒乓球在碰到桌面后会改变运动方向，表明力可以改变物体的运动状态
C.
击球时球拍对乒乓球的力大于乒乓球对球拍的力
D.
乒乓球在空中飞行时不受力的作用
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