With ________ look of disappointment, he left the Student Union office. Without ________ knowledge of photographing, he missed the chance to be an editor of Babel.

A．the, the

B．a, a

C．the, a

D．/, the

钟表：时光

A．潜艇：深度
B．铅笔：素描
C．毛衣：温暖
D．天平：质量