To learn swimming well,one needs much practice.哪个是主句,哪个是从句,怎么判断?到底有没有从句?这句句子算不算主从句?

问题描述:

To learn swimming well,one needs much practice.哪个是主句,哪个是从句,怎么判断?
到底有没有从句?这句句子算不算主从句?