Word Usage – ‘Are Not Prepared’ vs. ‘Haven’t Prepared’: How to Choose?

I'm not a fan of Ngrams, so my answer is based on personal opinion and experience.

Although I suppose that the three phrases would be perfectly understood in context, if I were to use one of them I'd go for the first one (I have no clue) or for a modified version of the second (I don't have a clue or I haven't got a clue).

I wouldn't use the second phrase as it is because in negative sentences the verb have is normally used either in conjunction with got, thus being an auxiliary, or preceded by "don't"/"doesn't"/"didn't" as any other verb.

As for clueless, OALD states that it is an informal, disapproving adjective which means "very stupid; not able to understand or do something", which is a deviation from the meaning of the previous sentences.

Anytime a person returns communication it can be called a response or a reply, while an answer is a form of response which is a solution to a problem or question. So response and reply are generic and can be used in any situation, while answer is more specific in its usage.

So if you asked a question or asked for a solution to a problem, and the person gave it to you, then you can say "Thanks for your quick answer". If it was not in one of these categories, then use response or reply since these are both generic.

And if you are still in doubt, remember that because response is generic you can use it in any situation.