The little boy can tell stories ()the age of 3.

问题描述:

The little boy can tell stories ()the age of 3.
()中写in,on,at

答案是 at
at the age of 3 = 3 岁,在3 岁时,早在 3 岁
at 是这个短语的固定介词.
The little boy can tell stories (at) the age of 3.
这孩子3 岁就会讲故事.
希望帮到了你,