题目

                              We had a math contest today. I am good at math, so I ___1____it quickly. I was the first one to _____2___ the paper. I was sitting on my seat relaxing, while the teacher shouted, Whose paper is this? I made no response. Some time later, I suddenly realized that I didn't sign my name on the paper. I stood up ____3___ and went to the teacher. She helped me find the __4____ paper and sign my name. I would have failed the contest if she hadn't ____5___me in time.(    )1.A. did        B. finished     C. worked       D.“凤凰”号火星探测器圆满完成任务，向地面发回数量堪称史无前例的图象和数据，为人类探索火星提供了宝贵的科学资料．（1）“凤凰”号探测发回的最新照片上显示，火星上确有液态水存在．微粒模型示意图可表示构成水的微粒的是______（填标号）．（2）火星上含有丰富的二氧化碳和镁资源．科学家设想，镁可作为未来火星上的燃料，因为镁能在二氧化碳中燃烧放出大量的热，同时生成氧化镁和碳．该反应的化学方程式为______ 2MgO+C