When I was leaving "The Truth", I asked my dad (the elder) this question: Is there any way possible that the witnesses might not be who they claim to be? He didn't even have to think about it, but answered, NO WAY. So I said, "Is it POSSIBLE for you to be wrong about that?", and he said, "no, it's impossible for them not to be who they claim to be".
This is how JW's believe. I believe any JW would answer the same way.
To say it's IMPOSSIBLE that you're wrong is the definition of being CLOSED-MINDED.
Since leaving the witnesses I have asked this same couple of questions to Mormons, Christian fundamentalists, Jews, etc about their own beliefs, and get the same response......
Everybody has the truth, just ask them and they will tell you!