"Who knows those doctors?"
Translation:¿Quién conoce a esos médicos?
More on the personal "a": it doesn't NOT translate into English but it is imperative when the object of a sentence is a person and even a pet. It is considered very impolite to leave it out. It is tough. I go for weeks getting it right and then my brain fries and it seems I can't remember to do it with my are twisted behind my back. Good luck! BTW the person who does the liking or loving (gustar and encantar verbs) is the object and needs the personal "a"