INLAND ONLY Your vessel is proceeding down a channel, and can safely navigate only within the channel. Another vessel is crossing your bow from port to starboard, and you are in doubt as to her intentions. Which statement is TRUE?

Correct Answer: Option D — The sounding of the danger signal is mandatory.

Under Rule 34(d), when vessels in sight of one another are in doubt whether sufficient action is being taken to avoid collision, the vessel in doubt must immediately sound at least 5 short and rapid blasts on the whistle.