题目

牙膏是人们生活的必需品，在牙膏生产过程中需加一种摩擦剂，这种摩擦剂是由一种矿石经下列变化制得的极细的粉末。     则该矿石M的主要成分最可能的组成为（    ）     A．MgCO3    B．MgSO3    C．CaCO3    D．CaSO3 答案：C 解析:CaSO3、MgSO3具有还原性，高温会变质为CaSO4、MgSO4而不分解。MgCO3分解生成的MgO难与水反应。书面表达假如你是Lingling, 你的美国朋友Betty要来中国旅游，她需要你的帮助，下面是Betty给你的一封信，请根据信的内容给她回一封电子邮件，80词左右，信的开头已给出，不计入总数.Dear Lingling,I’m preparing for a trip to China, and I’m making a list of things for my trip, but I don’t know what I should take? I’m leaving at the end of August. I’m going to stay there for three weeks, what clothes should I take? Which places of interest can I visit? What else should I pay attention to? Can you give me some advice?YoursBettyDear Betty,I’m very happy that you can come to China for a trip. _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________YoursLingling