Miss Li _______ as a secretary for five years in the company, and now she is general manager of it.

A．serves

B．served

C．has served

D．had served

与CT扫描伪影无关的是（）。

A.扫描中病人的移动

B.显示器故障

C.探测器故障

D.体内有金属异物

E.扫描层面中有高密度骨出现