who
I don't know who made the cake.
I don't know who killed him.
No sé quién salió de aquel sótano, pero no fue Dave.
I don't know who came out of that basement, but it wasn't Dave.
— Mystic River (2003)
I don't know who should do it.
I still don't know who should do it.
No sé quién ganó el campeonato.
I don't know who won the championship.
I don't know who killed her.