課本中不會教你的[A]90　at the age of和by the age of

90　at the age of和by the age of

① at the age of意為“在……歲時”，表示一個時間點。

He began to study English at the age of three. 他在3歲時就開始學(xué)英語了。

She went abroad with her father at the age of ten. 她10歲時同父親一起去國外了。

② by the age of意為“在……歲之前”，表示截止到某一時間之前，如果by the age of在句中指過去時間，謂語動詞要用過去完成時。

He had read many novels by the age of fifteen. 在15歲前他就讀過許多小說了。

By the age of ten，she had learned to play the violin. 在10歲前，她就學(xué)會拉小提琴了。