题目：
| 完形填空。 | ||||
| Christmas is for giving and sharing, for getting together with family and friends. But mostly it's for love. I had not believed this until a student, who was called Mark, gave me a wonderful gift one Christmas. Mark was an ll-year-old orphan (孤儿) who lived with his aunt, a middle aged woman greatly annoyed (使 烦恼) with the burden (负担) of 1 for her dead sister's son. I had not 2 Mark especially until he began staying after class each day to help me tidy up the room. We did this quietly, not speaking much, but enjoying the time of the day. When we did talk, Mark spoke mostly of his 3 , who had alwaya spent much time with him before she passed away. 4 Christmas came near, however, Mark failed to stay after school each day. I 5 him one aftemoon and asked why he no longer helped me in the room."I was making you a 6 ," he said confidently (有信心地) in a low voice. "It's for Christmas." With that, he left the room in a hurry. He didn't stay after school any more after that. Finally 7 the last school day before Christmas. Mark walked slowly into the room late that aftemoon."I have a present," he said. "I hope you like it." He held out his hand, and in it wasa tiny wooden box. "It's beautiful, Mark. What's in it?" I asked, opening the top to look 8 . "Oh, you can't see it," he replied," and you can't touch it, or taste it or feel it, but mother always said it makes you feel good all the time, warm on cold nights, and safe when you're 9 . "I looked into the 10 box. "What is it, Mark," I asked, "that will make me feel so good?" "It's 11 ," he said softly," and mother always said it's best when you give it away." And he tumed and quietly left the room. So now I 12 the small box on the piano in my living room. Yes, Christmas is for joy, songs and nice gifts, but mostly, for love. | ||||
|
答案：
1-6 CDABDC 7-12 CBABAD
2CaO+O2↑+2xH2O，得到O2在标准状况下体积为672 mL，该样品中CaO2的物质的量为_____。