After serving as a soldier in Iran for five years, he ____ a new job in Seoul as a driver.

A．took up

B．kept up

C．saved up

D．drew up

硫酸-硝酸消化食品样品过程中，要维持定量的硝酸是（）

A.使样品灰化

B.缩短消化时间

C.避免发生炭化还原金属

D.除去干扰杂质

E.为了消化完全