我不知道他們為什麼在打架。

I don't know why they are fighting.

Source: Tatoeba

Sentence Composition

1 我不知道 wǒbùzhīdào I don't know.
2 他們 tāmen they; them
3 為什麼 wèishénme
  1. why?
  2. for what reason?
4 在 zài
  1. to exist; to be alive
  2. (of sb or sth) to be (located) at
  3. (used before a verb to indicate an action in progress)
5 打架 dǎjià
  1. to fight
  2. to scuffle
  3. to come to blows

classifier: 場