问题
选择题
He was still working on his project while other people ______ a rest. [ ]
A. were having
B. are having
C. will have
D. have
答案
答案：A
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He was still working on his project while other people ______ a rest. [ ]
A. were having
B. are having
C. will have
D. have
答案：A
、长为
的木板右端水平固定有一轻质弹簧，在板上与左端相齐处有一质量为
的小物体（
，
），木板与物体一起以水平速度
向右运动，若