(2013·吉林长春三校高三调研)I started as ________ office clerk, and turned ________ department manager three years later.

A．the; the

B．an; a

C．an; /

D．the; /

防水涂料施工，胎体增强材料的选用应与涂料性质相匹配。选用时，如酸碱值(pH值)小于7的碱性涂料，则应选用无碱的玻璃纤维产品。( )