Chat like a Chinese

The best way to speak a language fluently is to communicate with native speakers. So what I want to share today is some of the most frequently used onomatopoeias in Chinese online chat.
While browsing, please answer a question: what are the characteristics of these Chinese characters?


1.“嗯嗯”（ènen）：Used as a sign of approval or satisfaction.  
For example：--Vicky, do you like blue?  
             --嗯嗯，I like blue.  
2.“哈哈”（hāha）：Nice, but (sometimes) not really funny.  
For example: -- You look good in this picture.  
        --哈哈，谢谢！  
3.“哈哈哈”（Generally more than two or three）”：Real funny / can't help to laugh／laugh out loud.  
   For example:-- The principal said that Greater Snow was coming down today, so the whole school was off!!!  
         -- Really? Great.!!!哈哈哈哈哈!!  
4.“呵呵”（hēhe）：An awkward response / piss off.  
   For example：-- Mirror, mirror, isn't I the most beautiful person in the world?  
             --呵呵…….  
5.“哦哦”（òo）：To show understanding or Indicating Understanding.  
   For example：--“爱” means “love”.  
            --哦哦！  
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*Have you thought about the question? Yes, the answer is the one you think.                
All Chinese characters have the left side of the mouth.*