Question: If it is not known or virtually certain that at least one of either the player, an opponent or an outside influence caused the ball to move, the Rules will assume that natural forces were the cause.
A) True (correct)
Explanation: The Rules make natural forces the default cause of movement of the ball. So unless it was clear (known or virtually certain) that something else caused the ball to move, it will be attributed to natural forces. See Rule 9.2b(2)