it is one of the most important reasons that i 'm fascinated by book that在从句中做什么成分呢
问题描述：
it is one of the most important reasons that i 'm fascinated by book that在从句中做什么成分呢
答
that是=why,引导定语从句.这种用法是较为口语化的.that作关系副词的时候可以引导时间,地点,方式,原因,距离,方向等等,取代when,where,why等关系副词.