题目

  The Best HolidayI was unbelievably proud of my nine-year-old daughter, Emily. 1 to buy a mountain bike, she’d been saving her pocket money all year, as well as doing small jobs to earn extra money.By Thanksgiving, she had collected only $49. I said, “You 2 have your pick from my bicycle 3 .” “Thanks, Daddy. But your bikes are so old.” She was right. All my girls’ bikes were 1950s models, not the kind a kid today would 4 choose.As Christmas 5 near, Emily and I went bike shopping. As we left one store, she 6 a Salvation Army volunteer standing next to a big pot. “Can we give s要判定一个命题是真命题，往往需要从命题的条件出发，根据已知的定义、公理、定理一步一步推得结论成立．这样的推理过程叫做 ．