---I heard your grandpa used to be a teacher.
--- Yes. He was a math teacher .
A. on the 1950s
B. in the 1950s
C. at the 1950’s
D. in 1950’s
网友回答
A. on the 1950s
(答案→)B. in the 1950s
C. at the 1950’s
D. in 1950’s
解析：考察年代表达。年份后面加上s，表示某个年代，故选项CD年代表达错误。表示时间时，on表示在具体某一天，in表示在一个时间范围。年代属于一个时间范围，故用介词in，选B。