When children live at school,they cannot rely on their parents any more and have to ...When children live at school,they cannot rely on their parents any more and have todeal with all problems by themselves.求问句子中为什么用“逗号”以及逗号前后两句分别是什么成分,还有个句子问题一样：After they are sent to boarding schools,they become lessdependent on their parents.

When children live at school,they cannot rely on their parents any more and have to ...
When children live at school,they cannot rely on their parents any more and have to
deal with all problems by themselves.求问句子中为什么用“逗号”以及逗号前后两句分别是什么成分,
还有个句子问题一样：
After they are sent to boarding schools,they become less
dependent on their parents.