(A)When the modifier (appositive or other kind of modifier) is purely descriptive, and not necessarily to establish the identity of the noun, it is non-vital, non-essential modifier, and these are ALWAYS separated by commas. 【如果修飾語的內容僅僅是描述型的,沒有涉及到被修飾語的根本的,就算沒有了這個modifier也可以知道noun說的是什麽的,一定要用comma!】