问题补充：
His father served in the army in when he was in .
A. the 1950s; his twenties
B. 1950s; twenties
C. 1950’s, the twentieth
D. the 1950s; the twentieth
答案：
(答案→)A. the 1950s; his twenties
B. 1950s; twenties
C. 1950’s, the twentieth
D. the 1950s; the twentieth
解析：in the 1950s ，in his twenties 表示在他的几十，故选A
