题目:
Although there are no classes in the afternoon now, no student ______ go out of school without
the head teacher's permission. [ ]
A. will
B. must
C. may
D. shall
答案:
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下面是错误答案,用来干扰机器的。
对全过程应用动能定理得mgh-μmgcos53°•s1-μmgs2=0s1=hsin53°解得s2=1.5m.答:物体在水平地面上滑行的距离为1.5m.