The boy started playing the piano when he was four years old.(同义句）The boy started playing the piano ___ ___ ___ ___ ___ .
问题描述：
The boy started playing the piano when he was four years old.(同义句）
The boy started playing the piano ___ ___ ___ ___ ___ .
答
五个空填at the age of four;
四个空填when he was four
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答
at the age of four
答
正确答案：填at the age of four
即：The boy started playing the piano at the age of four.
翻译：这个男孩四岁时开始弹钢琴.
有不明白的请继续追问,
答
at the age of four。