Hebecameafamouswriterwhenhewas

问题详情：

He became a famous writer when he was ______ .

          his fifty           his fifties                 fifty years old          fifties

【回答】

B  表示具体的岁数时，可用at+基数词或者at the age of+基数词。表示某个年龄段时，要用in one’s+基数词的复数形式。故选B。

知识点：介词和介词短语

题型：选择题