Well, generally speaking we consider that THE solution of a MCQ where penalty for wrong ticks is clearly indicated, to be the whole ticked/unticked binary vector: anything else than this very vector is wrong and worth 0 points. (the reason being: if you know that there is some penalty for wrong ticks, simply don't tick propositions your are not sure of). We generally want to evaluate the total/global understanding of a given point, not a partial understanding of it.
Now, in some cases we could consider some wrong answers to be "less wrong" than others and could weight them a bit less than "completely wrong" (= kill the whole question), as we could also consider some positive answers (the most trivial ones) to be less weighted than others.
