【选做题】科学家发现，在月球表面没有空气，且重力加速度约为地球表面的
，若从月球上空同一高度同时释放氢气球和铅球（忽略地球和其他星球对月球的影响）则（ ）1 6
A．氢气球和铅球的质量都减小
B．氢气球加速上升，铅球加速下降
C．氢气球和铅球同时下落，且同时落到月球表面
D．氢气球和铅球同时下落，但铅球先下落到月球表面
A、质量不会随外界环境的变化而变化，故氢气球和铅球的质量都不变，故A错误；
B、由于月球表面没有空气，故两球均只受月球的引力，在月球上做自由落体运动，故两球均加速下降，同时落到地面上，故B、D错误，C正确；
故选C．
| 英英匹配。 |
| （ ）1. Who is younger than Grandfather?. （ ）2. What did you do on Monday? （ ）3. How do you spend your weekend? （ ）4. Are you as tall as your brother? （ ）5. Who' s Jimmy? （ ）6. How many chairs are there in your classroom? （ ）7. Who jumps higher than Li Ping? （ ）8. Do they look the same? （ ）9. Su Yang has a twin sister. （ ）10. What did Ben do on Sunday morning? | A. Grandmother is, I think. B. I take photos. C. We visited a farm. D. Really ? That's interesting. E. He went for a walk. F. That's Jack's dog. G. Twenty-four. H. Yes, they do. I. Yes, I am. J. Wang Fang. |