Answer:
The correct answer is: not an opinion.
Step-by-step explanation:
An opinion is a thought or belief about something that is ambigious, meaning that one can either support of reject the idea.
However, it is a fact that no matter how fast a human flaps his arms, they will never be able to fly.
When a sentence is factual, one cannot chose to agree or disagree with it. Therefore, this phrase is not an opinion, but a wrong statement.