问题补充:
---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
答案:
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。