Is it the best answer or the one I liked the most? I am really confused between two answers. Some of them are simple and clear, a second is informal.
Is there a way to close my question without choosing an answer?
The answer you choose is completely up to you. No one can select an accepted answer for you, not even moderators.
You choose the answer that solved your problem and worked best for you. You alone know exactly what you were trying to solve and only you can select the answer.
The most upvoted answer is the one the community likes the best, but that doesn't mean it solved your problem the best. This way people can see what answer solved your problem or what you choose and they can see what is popular with other people at the same time.
If no answer is acceptable to you, then don't select one yet. It is ok to not accept an answer if you are not sure. I would say do not close your question if it hasn't been answered completely. It may take a while before a person that knows the subject matter well finds your question. Also, others might find your question and the answers provided so far useful.
Pick the most correct answer that helped you with your problem.
I think it's important to pick from those answers that are solidly correct. It doesn't do any good to give the stamp of approval to answers with errors, because that will just mislead other people who come to the site and look at the first (green, selected) answer.