My father served in the army in when he was in .A. 1950’s; twentiesB. the 1950s; his twen

问题补充：

My father served in the army in when he was in .

A. 1950’s; twenties

B. the 1950s; his twenties

C. 1950’s; the twenties

D. 1950s; the twenties

答案：

A. 1950’s; twenties

(答案→)B. the 1950s; his twenties

C. 1950’s; the twenties

D. 1950s; the twenties

解析：考查数词。In the 1950s/1950’s在20世纪50年代；in one’s twenties在某人20多岁时。句意：我父亲参军是在20世纪50年代，那时他20多岁。