How to react when a good answer answers the opposite direction that the question asks?

Question

What are the advantages of a paper dictionary over an online dictionary?

The question asks for the advantage of paper dictionary over an online dictionary. However, the answer in the link mostly discusses about the advantage of online dictionary over its paper counterpart. I don't know how to react to this answer. Should I:

• Upvote it if I find it useful?
• Downvote it if it doesn't answer the question?
• Comment on it? But I don't have anything to comment.
• Flag it? I am flagging it here in the meta.

Answer 1

If it doesn't directly answer the question, downvote the answer if you feel it is deserving of it.

Leave a comment so that the answerer realizes why their answer was downvoted several times. Hopefully, this will encourage the answerer to keep on-topic in the future.

Flag for moderator attention as well, if you feel that the answer is entirely unrelated to the question.

Answer 2

If an answer doesn't answer the question, you should:

1. Downvote
2. Comment

This question on Meta.SE addresses a similar issue.

Answer 3

I think it indeed answered the question. But the answerer didn't write/forgot to write "I don't agree with you. I think It's the online version that has advantages over the paper one" in the first line. If he had done this, everything would be okay.