问题
选择题
While we were watching the play, I____noticed a man with a funny look.[ ]
A. usually
B. suddenly
C. quickly
D. carefully
答案
答案：B
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While we were watching the play, I____noticed a man with a funny look.[ ]
A. usually
B. suddenly
C. quickly
D. carefully
答案：B
的速度向斜上方抛出，，不计空气阻力，石块落地时的速率是 m/s；若石块在运动过程中克服空气阻力做了73.5J的功，石块落地时的动能为 J。（
）