the first language that you learn when you are a baby， rather than a language learned at school or as an adult。
Make A Little Progress Every Day 每天进步一点点昨天学习了eat one's words，今天我们再来学习一个和 word相关的高频习语~No.1 You have my word. 我说到做到/我向你保证。A: I'll do my best.
