The statement "he can see nothing, can he?" sounds extremely unnatural (or like something someone would say when speaking extemporaneously), and it's a bit confusing even for me, but the most logical answer to an English native speaker would be: B. No, he can't. He is blind. A major clue is the tag question, "can he?" (not "can't he?"). The answer is "no, he can't." A better test question would be "He can't see anything, can he?"

B is the right option.