—Must I arrive at school at one o'clock in the afternoon?   

—No, you_______.    [ ]

A. mustn't      

B. needn't    

C. can't        

D. shouldn't

X线检查肺动脉段凹陷（）

A.动脉导管未闭合并肺动脉高压

B.室间隔缺损

C.房间隔缺损

D.法洛四联症

E.动脉导管未闭