One day Skygirl went to our classroom with Skyboy. She was very h____. She took a hamburger and a cola w____ her. She wanted to r____, to have some food and drink and t____ to boys and girls in the classroom. She was not happy when she saw the s____ in the classroom. What does the sign mean? It says: "Don't run in the classroom. Don't talk to each other in class. Don't ear or d____ in class. ""I don't want to be in the classroom. Let's f____ away. "The Supergirl said to the Superboy. They came to the Garden City. Garden City is an i____ place for the Superchildren to play.

按一定的特点或规律对物质进行分类，给化学学习与研究带来很大的方便．下列各组物质中，符合“氧化物﹣酸﹣碱﹣盐”顺序排列的是（    ）

如图甲所示，光滑金属导轨MN、PQ所在平面与水平面成θ角，M、P两端接一电阻R，整个装置处于方向垂直导轨平面上的匀强磁场中．t=0时对金属棒施加一平行于导轨的外力F，使金属棒ab由静止开始沿导轨向上运动，导轨电阻忽略不计．已知通过电阻R的感应电流I随时间t变化的关系如图乙所示．下列关于棒运动速度v、外力F、流过R的电量q以及闭合回路中磁通量的变化率 $\frac{\Delta \varphi }{\Delta t}$ 随时间变化的图象正确的是（   ）