求解：为什么选B，（答案是B）搞不懂这个，谁可以帮我看看是怎么回事吗？谢谢。

Question

his father began to work___he was seven years old
a as old as
b as early as
c since
d while

Answer 1

as old as :和......一样老
as early as:早在......时候
since:自从.....以来（多用于现在完成时）
while:然而
所以，答案就一目了然了