If someone nearly has no knowledge about the topic a question has been asked on but they still irresponsibly answer it or comment on it without understanding question properly, what would be the best response from the person who asked question.
Just flag for admin to look at it, and we will
This sometimes happens, but please don't make an offensive riposte. That almost always starts a flame war which just adds noise to our site. Just respond politely or, if appropriate, flag for moderator attention.
Not everyone is an expert. You may think they are being irresponsible but they may be genuinely trying to help - give them the benefit of the doubt.
Isn't that what comments and downvotes are for? I would only think to flag for moderator if it was spammy ("Check out my barely related blog post!") or well beyond wrong and into suggesting things that are downright dangerous ("Just type format c: into the command prompt!")
Personally: If your answer is simply useless to the question (you missed a point completely), you get a down-mod and a comment on why.
If you made a valiant effort at least, but came up short I'll probably just leave your answer alone. Maybe put in a comment as to what you need to do to become "the answer".
If you are dangerous, you're getting flagged, with a comment underneath on "PLEASE DON'T TRY THIS ANYONE!" until an admin comes along and cleans up.