Add subject or NOT????
When we say 他告诉他的爸爸ABC ／他问他爸爸ABC I think sometimes we have to add subject and sometimes you omit. Can someone explain about this process? When can you omit and when do you have to add? 在那个情况下／什么时候省略主语呢？？？

高文中告诉医生他肚子疼死了
我告诉他吃药
医生问他他发不发烧
医生问他他有没有发烧？
他问我我想不想去她家。
他告诉我我应该走。。。等等

Question

Add subject or NOT????
When we say 他告诉他的爸爸ABC  ／他问他爸爸ABC   I think sometimes we have to add subject and sometimes you omit.  Can someone explain about this process?  When can you omit and when do you have to add? 在那个情况下／什么时候省略主语呢？？？

高文中告诉医生他肚子疼死了
我告诉他吃药
医生问他他发不发烧  
医生问他他有没有发烧？
他问我我想不想去她家。
他告诉我我应该走。。。等等

Answer

the subject could be omitted
But the meaning of sentence may be different.

for intance:我告诉他吃药

我告诉他（我）吃药
他：what are you doing？
我：i take the medicine.

我告诉他（他）吃药
i told him that he should take the medicine.= i told him to take the medicine.

Answer

这个嘛，多看多练多说吧。
当你在转述别人的话时，后面从句的主语就可以省略。中文中确实存在很多不需要用到主语的句子。主要是因为这个主语在先前的句子中提到过了。