If you travel by _______ train, you can have quite a comfortable journey, but make sure you get ______

fast one. [      ]

A . the ; the    

B. 不填 ;a        

C. the ;a        

D. 不填;不填

间隙感染脓肿形成后，下列间隙均可作下颌下缘下切口，除了

A．下颌下间隙

B．眶下间隙

C．翼下颌间隙

D．口底蜂窝织炎

E．咬肌间隙