Any answer could be correct; but some answers may not be correct.
Any of the fruit in the basket could be bad; but some of the fruit will be good to eat.
Any of us can make an occasional mistake; but some of us make mistakes all of the time.
Any answer could be correct, but some of us will make a mistake in our answer.
Some people may not have all of the answers, but at any given moment, it is true that many will offer correct answers.