题目

词汇 ；根据句意和汉语提示写出单词，完成句子。 1. My cousin used to be very interested in ____________  (收集) postcards. 2. The dentist suggests that we should brush __________(牙齿) three times a day. 3. He lost his iPad last ___________(星期三).  He was very sad. 4. Armstrong joined the navy in 1949 and served as a _______ (飞行员) for three years. 5.___________ (比较) with life on the Earth, life on Mars would be better in some ways.在做“绿叶中色素的提取和分离”实验时，甲、乙、丙、丁四位同学使用相关试剂的情况如表所示（“+”表示使用，“﹣”表示未使用），其余操作均正常，他们所得的实验结果依次应为（ ） 甲乙丙丁丙酮﹣+++水+﹣﹣﹣CaCO3++﹣+SiO2+++﹣A.①②③④B.②④①③C.④②③①D.③②①④