If we have no list of choice, we say:
What thing do you know?
If the list of choice appears, for example "of these ones", we change "what" for "which":
Which thing of these ones do you know?
But what to do if we deal with alive nouns?
An example without the choice list:
What person do you know?
What if we add "of them". Does "what" have a variant for the choice of list for alive nouns like "which" for not alive ones or it would be "which' anyway?
Which person of them do you know?