Dela had made up his mind to give it up ,but on _____ second thought ,he determined to try ______ third time．

A．/; a

B．/ ; /

C．a ; a

D．the ; a

作口腔颌面X线检查时，下列选择正确的是（）

A.根尖周囊肿常用横断牙合片检查

B.下颌较大的囊肿首选根尖片

C.观察关节间隙改变首选用髁突经咽侧位

D.鼻腭囊肿常用牙合翼片

E.怀疑上颌窦炎首选华氏位片检查