E. Le 了 is used to ask or answer general questions about who did something without requesting specific information about quantity, duration and so on. For example, the speaker would ask who bought books instead of who bought three books, or who drank wine instead of who drank two glasses of wine.

    1. Shéi mǎi shū le?
      谁买书了？
      Who bought books?


    2. Wǒ mǎi (shū) le.
      我买（书）了。
      I did. (I bought books.)


    1. Shéi qù Zhōngguó le?
      谁去中国了？
      Who went to China?


    2. Tā qù (Zhōngguó) le.
      他去（中国）了。
      He did. (He went to China.)

      3. Note that if specific information is sought, the sentence must use verb-suffix le 了 instead of the sentence-end le 了.


    1. Shéi hē-le liǎng bēi jiǔ?
      谁喝了两杯酒？
      Who drank two glasses of wine?


    2. Wǒ hē-le liǎng bēi jiǔ.
      我喝了两杯酒。
      I did. (I drank two glasses of wine.)