Hebecameafamouswriterwhenhewas

問題詳情：

He became a famous writer when he was ______ .

          his fifty           his fifties                 fifty years old          fifties

【回答】

B  表示具體的歲數時，可用at+基數詞或者at the age of+基數詞。表示某個年齡段時，要用in one’s+基數詞的複數形式。故選B。

知識點：介詞和介詞短語

題型：選擇題