在“用电流表、电压表小灯泡测电阻”的实验中，滑动变阻器不能起到的作用是A．改变电路中的电流B．改变被测电阻的阻值C．改变被测电阻两端的电
建设资源型和环境友好型社会，必须强化全民族的环保意识和节约意识。这是因为 (1)实践是有意识、有目的的活动 (2)主观能动性决定事物发展的方向 (3
_____，there were also no lights in the houses along the street． A．There not only were no streetlights B．Not only there were no streetlights C．Not onl
金属A、B跟质量相同、质量分数相同的稀硫酸反应，生成氢气的质量与反应时间有右图所示关系（已知：A、B在生成物中均为+2价）。则下列结论中，不
下列说法正确的是 ( )A、难溶于水的电解质一定是弱电解质B、易溶于水
Parents whose children show a special interest in a sport feel very difficult to make a decision about their children’s careers．Should they allow their children to train to become top sportsmen an
One day when Jack was walking in the park, he saw a woman, who lived a few miles away, sitting on a bench with a dog beside her. The dog was looking up at the woman. Jack walked up to the wo
一物体在竖直方向的升降机中，由静止开始竖直向上作直线运动，运动过程中小球的机械能E与其上升高度h关系的图象如图所示，其中0～h1过程的图线为
的定义域是 .
；
，解得
，因此定义域为