What does "なのか" mean in 彼女 が 誰 なのか わかりますか?


彼女 が 誰 なのか わかりますか。is a question which has 2 "ka" question markers? or is it 2
questions? (Could it be translated as who is she? you know? ) And what does
the "なの" means here? I think I've heard other phrases with "なのか" and I dont
know when it has to be used

