某同学身高1.6m,立于一大平面镜前,若该同学离镜面2m,则人和像之间的距离是_____m,像高_____m,若该同学向后移动3m,则像离镜子的距离为_____m。
4;1.6;5
用天平测量物体质量时,移动标尺上的游码相当于向天平______盘里______.
My cellphone has disappeared. Who ________ have taken it away?[ ]
A. could
B. should
C. must
D. ought