This is _______ difficult problem that few students can work it out. [ ]

A. so

B. so a

C. such

D. such a

不是颈部CT扫描适应证的是（）

A.颈总动脉狭窄或扩张

B.气管炎

C.甲状腺肿瘤

D.舌骨骨折

E.淋巴结肿大