His ambition is ______ an actor. [ ]
A. becoming
B. become
C. to become
D. became
C
在10000km2的海域中有40km2的大陆架贮藏着石油,假如在海域中任意一点钻探,钻到油层面的概率是( )。
抑制脉冲干扰,使用______电路是最有效的。