at the age of three 和 by the age of three有什么区别

一些关于介词的用法at the age of by the age of有什么区别 "by the age of","at the age of"的区别? in the age of by the age of at the age of的区别 by the age of 和at the age of的区别 He ____　read ______ write at the age of three. 请问一下at the age of 与 by the age of 的区别. by the age of the three of 和 three of 有什么区别? at the age of by/at the age of分别使用什么时态 The boy began to play chess at the age of three.（改为同义句） The He wants【 to live in the big house 】at the age of three【时间状语