--Is there any relationship _______ smoking and health? ---Sure. People who do not smoke usually enjoy a longer and healthier life. A. among B. within C from D. between 答案:D用图甲、乙两种方式匀速提升重为100N的物体,已知滑轮重20N、绳重和摩擦力不计.则( )A.手的拉力:F甲=F乙;机械效率:η甲=η乙B.手的拉力:F甲<F乙;机械效率:η甲<η乙C.手的拉力:F甲>F乙;机械效率:η甲<η乙D.手的拉力:F甲>F乙;机械效率:η甲>η乙