Who... ? Figure of speech Erotesis.
who... ? The Ellipsis is thus correctly supplied.
Related Commentaries of Jeremiah 9:12
Jeremiah 9:12
12 Who is the wise man, that may understand this? and who is he to whom the mouth of the LORD hath spoken, that he may declare it, for what the land perisheth and is burned up like a wilderness, that none passeth through?