题目内容：

he looks younger ,but he is older than me -three years.
A,since B,for C,about D,by

优质解答

选D [他看起来很年轻,但他比我大三岁.]
注释：by可表示“（数量或程度）达到”,用于数词前,又如：They overcharged me by 3 dollars.他们多收了我3美元.