—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

我国大肠癌最多发的部位在

A．直肠

B．横结肠

C．盲肠

D．降结肠

E．升结肠