如图所示，ef，gh为水平放置的足够长的平行光滑导轨，导轨间距为L=1m，导轨左端连接一个R=2Ω的电阻，将一根质量为0.2kg的金属棒cd垂直地放置导轨上，且与导轨接触良好，导轨与金属棒的电阻均不计，整个装置放在磁感应强度为B=2T的匀强磁场中，磁场方向垂直于导轨平面向下．现对金属棒施加一水平向右的拉力F，使棒从静止开始向右运动．试解答以下问题．

使用显微镜时，“观察”操作步骤正确的是（    ）

①左眼向目镜内看，右眼也要同时睁开；

②眼睛看着物镜转动粗准焦螺旋，使镜筒缓慢下降至物镜接近玻片标本为止；

③把要观察的玻片标本放在载物台上，用压片夹夹往；

④反方向转动粗准焦螺旋，使镜筒缓缓上升；

⑤略微转动细准焦螺旋．

完形填空

      Hey, I'm Simon. I have a strong and faithful dog, Bruce. The dog likes1with me. Sometimes he also follows my father to work. One morning when my father worked in the field, he2 his coat and put it under a big tree. He turned  to the dog and said,“3my coat, Bruce!” Bruce sat down on the coat. Later, my father remembered he had to buy some food.  4 he hurried to the shop.   5 shopping, he went home directly and forgot completely about his 6 and the dog. In the evening, I looked for my dog7 in the house, but I8 find him. At this time, my father suddenly remembered his coat and the dog. He went back to the tree   9. He found that Bruce was 10 sitting on the coat!

①恢复公民大会作为国家最高权力机关

②实施“陶片放逐法”

③组成“四百人会议”执掌最高统治权

④确立财产等级制度

我国自己修建的第一条铁路是____，是____主持修建的。