题目

阅读下面短文，掌握其大意，然后从各小题所给的四个选项中选出最佳选项。It was Raj’s first day of school in a new country. He was very nervous, ____ his family just moved to the United States from India.“Welcome, Raj,” his new teacher Mr. Washington reached out his hand. Raj ______ it as his father told him. A boy with a big smile walked over. “Raj, this is Sandeep. _____ will help you during the school day.” “Namaste (有礼了),” Sandeep said. He placed his hands together as he bowed.“Please, take a seat,” Mr. Washington said as he pointed to a请你通过生活经验和回忆所学知识，归纳哪些反应能生成氧气，试着写出这些反应的文字表达式．然后分析这些反应能否用于实验室制取氧气．并说明理由．（提示：实验室制取气体的原料选择应考虑操作是否简单、反应条件是否很难达到、所产生的气体是否便于收集、反应原料是否易得等因素．）生成氧气的反应的文字表达式能否用于实验室制取氧气及理由1______氢气+氧气