A good friend of mine from when I was born showed up at my home right before I left for Beijing.

参考译文：一个自我出生之时起就是我好朋友的人在我动身前往北京之前出现在我家里。

A．how B．whom C．when D．which

备注：from when I was born的语法结构为：为介词from+when宾语从句。介词from +when 宾语从句构成介词短语在句中作后置定语，修饰前面名词短语a good friend of mine。介词from相当于since。即from when...相当于since when...

A good friend of mine from when I was born 【主语】//showed up【谓语动词】// at my home right【地点状语】// before I left for Beijing【时间状语从句】.

A good friend of mine 【中心词】// from when I was born【后置定语】

备注：中心词a good friend of mine(我的一个好朋友)在主句中作“主语”，from when I was born(自从我出生起的) 为介词短语作后置定语修饰名词短语a good friend of mine。

类似于网友提供句子如下

Her memories start from when she was five.她打5岁起就记事儿了.

From when he was a young man, he had suffered from a chronic lung illness.

从他年轻时起, 他受到慢性肺部疾病的折磨.