为什么说Devotion is important to success,为什么用介词to

为什么说Devotion is important to success,为什么用介词to It is important to us为什么用介词to to help...为什么要用介词to? 为什么说be used to doing 的"to"是介词? It is important for us to learn English well. 为什么用to learn是用 Health is very important to us.为什么用to而不用for呢?呵呵, This is very important ( to ) me 为什么用To 而不用 for 用devotion to ,answer to ,approach to,damage to造句 water is important ___ people's life.用for 还是用to为什么?急 It is important to help people who no money.这里为什么用have?who后面 we show how important it is to keep learning .为什么important To study English is important ___you.(填介词)