—Mr. Wang ______ be on the playground, I think.

—He ______ be on the playground. I saw him in the office just now. [ ]

A. may; may not

B. can; mustn't

C. must; couldn't

D. may; can't

图有甲、乙两个质量相同的物体分别悬浮在水面下1m和2m深处，由此可以判断 

A．甲物体受到的浮力大于乙物体受到的浮力

B．甲物体受到的浮力等于乙物体受到的浮力

C．甲物体受到的浮力小于乙物体受到的浮力

D．无法判断