Your doubt is valid, but it is not required for GMAT. I know it's bizarre, but that's how GMAT works sometimes. So, area in any unit is fine. B is correct.
thanks fluke....I guess sometimes one has to face ambiguous questions, at least one may feel so. I hope i dont face such a question on test. i did in fact almost lock the answer choice B but at very last second idea came that without a standard measure unit the answer will make no sense. this was last question of kaplan
practise test 2 (linear).