IV. Declarative sentences
  1. When the main verb does not have an object.

    subject + verb + complement + le 了


    Wǒ chīwán le.
     我吃完了。
    I finished eating. I ate.

  2. When the main verb takes an object which does not have a modifier.

    subject + verb + complement + simple object + le 了


    Wǒ chīwán fàn le. 
    我吃完饭了。
    I finished eating (the food/meal). I ate (the food/meal).

  3. When the main verb takes an object which has a modifier.

    modifier + object + subject + verb + complement + le 了


    Nèi gè wèntí wǒ huídáduì le. 
    那个问题我回答对了。
    I answered that question correctly.