The correct answer is A) exchanging whistle signals if passing within half a mile. In inland waters, the Navigation Rules require power-driven vessels meeting head-on to exchange whistle signals to indicate how they will pass each other safely. This applies when the vessels are within half a mile of each other. The rules do not require the outbound vessel to be given the right-of-way (B is incorrect), nor is there a requirement to keep to the port side of the channel (C is incorrect). Stopping and waiting for the outbound vessel to initiate signals (D) is also not necessary, as both vessels have an equal responsibility to exchange signals.