| 不定项选择 |
| 万有引力定律的发现实现了物理学史上的第一次大统一“地上力学”和“天上力学”的统一。它表明天体运动和地面上物体的运动遵循相同规律。牛顿在发现万有引力定律的过程中将行星的椭圆轨道运动假想成圆周运动；另外，还应用到了其它的规律和结论，其中有（ ） |
A．牛顿第二定律 B．牛顿第三定律 C．开普勒的研究成果 D．卡文迪许通过扭秤实验得出的引力常数 |
ABC
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| It was two days before Christmas, when my ten-year-old Almie Rose told her father and me that she wanted a new bike. Her bike was too 1 , and it needed repairing as well. As Christmas 2 , her dream for a bike seemed to disappear, we thought, for she didn't say it again. We were busy 3 some beautiful story books, a doll house, a holiday dress and toys. Then to our surprise, on December 24, she said she really wanted a bike more than 4 . Now we didn't know 5 to do. It was just too late. We were busy with Christmas dinner and packing 6 presents, parents' presents, a brother's present and friends' presents till midnight. So there was 7 time to take to buy the "right bike" for our little girl. Thinking we were parents who would make their child unhappy, we felt sorry and 8 . Suddenly my husband had an idea. "What about making a little bike with clay (mi) and writing a note that she could trade in (交换) the model bike for a real one?" So he spent the next five hours carefully 9 with clay to make a small bike. 10 Christmas morning, we were so excited for Almie Rose to open the little box with the beautiful red and white clay bike and the note. She opened and read the 11 loudly. She looked at me and said, "So, does this mean I can trade in this bike for a real 12 ?" Smiling, I said, "Yes!" Almie Rose had tears in her eyes when she replied, "I would 13 trade in this beautiful bike 14 Daddy made me. I 15 keep it than get a real bike. This is the best Christmas present I have ever got in my life!" | ||||
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