It was on the farm where my father used to work that I was born.

为什么用where，而不是 that

这句的结构是强调句型

原句是I was born on the farm where my father used to work
这里当然用where，引导地点状语从句。这里的where不能换成that，也不能换成which，因为where的含义在这里就是on which

再对on the farm 进行强调，就成了
It was on the farm where my father used to work that I was born.

where这里引导定语从句，修饰前面的farm。 至于强调句的that在后面呢（that I was born）。 我正是在我父亲曾经工作过的农场出生的。

work 或者towork都可以

help有help sb do 和help sb to do 两种形式

where my father used to work 修饰farm 而work是不及物动词，所以不能直接修饰farm 所以不能用that 你可以说 the farm that my father used to work in 或者 the farm in which my father used to work