My friend Jack is from _____European country.We all think he is____honest boy.

A．a, a

B．a, an

C．an, an

D．an, a

食管的第2个狭窄在（）

A、与左主支气管相交处

B、距中切牙15cm

C、穿膈肌食管裂孔处

D、距中切牙40cm