「誰かいないのか」most likely means "Is anyone here?" without further context. It's the kind of thing you'd say if you walked into an empty room expecting to find someone, but there was no one there.
いないのか is just a questioning form of いない. It's very casual but has a bit of urgency to it. It's kind of like saying "Isn't there someone here?!" or "Anybody home?!"
First of all, A and C are out of the question as neither one logically fits the context.
From my personal experience with Japanese-learners, I know many of them would think B was correct, but it is not. B is "...