问题
选择题
—Listen! Is Professor Johnson giving a report in the hall?
—No, it _____ be him. He has gone to Japan. [ ]
A. needn't
B. may not
C. mustn't
D. cannot
答案
答案：D
搜题请搜索小程序“爱下问搜题”
—Listen! Is Professor Johnson giving a report in the hall?
—No, it _____ be him. He has gone to Japan. [ ]
A. needn't
B. may not
C. mustn't
D. cannot
答案：D
的光滑绝缘斜面处于水平向右的匀强电场中．一电荷量为+q、质量为m的小球，以初速度v0由斜面底端的M点沿斜面上滑，到达斜面顶端N的速度仍为v0．则