Question

he began to work THERE( ) A.on his fifty B.at age of fifty C.when he fifty D.in his fifties

说原因

Answer 1

选D：在某人多大岁数，通常有两种表达；
第一：in one's +年龄
第二：at the age of +年龄
B项少个the,所以只有D项是对的了。