问题
选择题
| It's sunny today. It's the best time _____ rockets. |
A. launch B. to launch C. launching D. launches |
答案
答案：B
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| It's sunny today. It's the best time _____ rockets. |
A. launch B. to launch C. launching D. launches |
答案：B
面5米处将一个质量为1千克的小球以10m/s的速度水平抛出, 若g取10m/s2，问