In any case however, this poem clearly demonstrates Frost's belief that it is the road that one chooses that makes him the man who he is.

【三个that的分析】

1. Frost's belief that：that引导同位语从句。即：that it is the road that one chooses that makes him the man who he is 是belief的同位语。

2. the road that one chooses：that引导定语从句。即that one chooses作定语，修饰the road。

3. it is the road ... that makes ...：是强调句式。the road为被强调的成分，that引导句子的其余成分。