.... She started saving for retirement in her early twenties. I think you have been reading bad ...
... your number.不加逗號,表示後面是原因。He left early , because I saw him left early .加逗號,表示後面只是消息來源...
...你的原句應該寫成: Since my sister had to take the train early next morning, Mom told her not to sleep late. 但是... 語言...