找出词类活用的词并解释
(1)木直中绳，车輮以为轮          ：                      
(2)君子博学而日参省乎己          ：                      
(3)上食埃土，下饮黄泉            ：                       
(4)假舟楫者，非能水也            ：                       
(5)假舆马者，非利足也              ：                     
(6)用心一也                      ：