The "right" answer would be B, but that's mitigated by the fact that choosing it would most likely go against the question itself. Since you're asked to pick at random, working the question out logically would make you fail regardless.
It is a good point AND I'm not positive any mitigation has to occur (though it might). I mean I think I get what you're saying & I do think this question is some kind of logical paradox. I mean why show us the answers or the number of answers if our selection occurs at random?
But no matter which choice is made or by what means that choice is made it will always be either right or wrong. That's 50%.
I don't know if that's the reasoning the quesioner is looking for, it's simply the reasoning I personally would offer. And, if my grade depended on that question, the teacher's car would have flat tires, a cup of sugar in their gas tank, & the end result of my gas station lunch on their hood & windshield.