(2013·南昌10所省重点中学二模)Mary ________ as a secretary in this company for twenty years and now she stays at home taking care of her own garden.

A．has served

B．had served

C．is serving

D．served

肺结核（）

A.X线呈大片状阴影，呈肺叶和肺段分布

B.X线呈大片状阴影，内有空洞伴液平

C.X线右上空洞，周围有斑片状阴影

D.X线右下偏心空洞，内壁凸凹不平

E.X线左下单个薄壁空腔阴影