か
ka
A fork in the road, still open: か
The picture A road splits in two and nothing has decided which way yet. Hand that undecidedness to the person in front of you and it's a question; leave it sitting inside your sentence and it becomes "I don't know". か hands the fork over because you genuinely don't know; ね rolls a ball over about something you do know, just to check you're standing on the same ground.