问题
选择题
Look! He with his students ______ playing football on the playground.[ ]
A. is
B. are
C. can be
D. can't be
答案
答案：A
搜题请搜索小程序“爱下问搜题”
Look! He with his students ______ playing football on the playground.[ ]
A. is
B. are
C. can be
D. can't be
答案：A
沿足够长的固定斜面上滑，斜面倾角为θ，物块与该斜面间的动摩擦因数
，下图表示该物块的速度v和所受摩擦力Ff随时间t变化的图线(以初速度v0的方向为正方向)中可能正确的是( )
