—Where is Zhang Hua? Is he in the classroom now?

—He          be there, for I saw him in the teachers’ office just now.

A．can’t

B．may not

C．shouldn’t

D．mustn’t

含牙囊肿囊壁附着在（）

A.牙冠中1／3

B.牙颈部

C.釉牙骨质界

D.根部

E.任何部位