I am an English girl. My name is Mary. I’m twelve. My dad and mom are English teachers. I have a brother（哥哥）. His name is Tom and he is thirteen years old. We are in China now. We are in Beijing No. 4 Junior High School. Tom is in Class 4, Grade 7 and I am in Class 9, Grade 7. I have a dog. My dog looks strong. It has a big mouth and two big black ears. We have many(许多) Chinese friends here. They are good.

某同学制氧气时，试管炸裂了，造成试管炸裂的原因可能是下列中的：①没有给试管均匀预热；②夹试管的铁夹夹的过紧；③试管外壁潮湿；④试管口没有向下倾斜；⑤忘了加催化剂；⑥试管没加棉花；⑦收集完氧气先撤酒精灯____ 

A．全部　　 B．①②④C．没有⑤D．没有②③

南沙群岛是我国传统渔场．这里的珊瑚礁里生活着许多品种的珊瑚虫，这种生物多样性的实质是（　　）

①该反应的生成物能量总和____（填“大于”、“小于”或“等于”）反应物能量总和．

②若2mol氢气完全燃烧生成水蒸气，则放出的热量____（填“＞”、“＜”或“=”）572kJ．

③与化石燃料相比，利用氢能源有很多优点，请说出其中一点____．