如图所示是一欧姆表(多用电表欧姆挡)的结构示意图，虚线框内有欧姆表的内部电路，红、黑表笔分别插入正、负插孔，虚线框内的欧姆表的内部电路图正确的是(  )

已知两瓶气体，分别是HCl和Cl₂．可以区别它们的方法或试剂是（   ）

①观察颜色 ②打开瓶盖看有无白雾 ③硝酸银溶液 ④湿润的红色石蕊试纸 ⑤湿润的蓝色石蕊试纸．

四年级有36人去游泳，共租了7条船，每条船都坐满了．大、小船各租了几条？

       Shenzhou X and three astronauts(宇航员) were sent up from Jiuquan Satellite Launch Center, Gansu province, into a clear blue sky on Tuesday, bringing the nation one step closer to building its own space(太空) station in 2020.
　　Two men, mission commander(指挥官) Nie Haisheng and Zhang Xiaoguang, and China’s second female astronaut, Wang Yaping, are expected to stay in space for 15 days.
　　They will teach young people about science and do two space dockings, between Shenzhou X and the unmanned Tiangong-1 space module, a technically difficult procedure that brings two spaceship together in high-speed orbit(轨道).
　　The trip is our country's fifth manned space mission, 10 years after the country’s first astronaut, Yang Liwei, went into space in 2003.

19世纪中期，在得克萨斯州，两个陌生人见面以手枪相对，他们的见面礼是一个老问题——“拥护奴隶制还是反对奴隶制”，跟在答话后面的往往是开枪。这说明（   ）