In narrow channels, vessels of less than 20 meters in length shall not impede the safe passage of vessels that can navigate only inside that channel.

• A. 10 Meters
• B. 30 Meters
• C. 40 Meters
• D. 20 Meters

Answer: (D)

In narrow channels, the aim is to protect the safe passage of vessels that can only navigate within that channel by ensuring smaller traffic doesn’t block them. The rule uses a clear length threshold: vessels shorter than 20 meters must not impede the passage of those channel-restricted vessels. That threshold—20 meters—defines who must yield or keep clear. If a vessel is 20 meters or longer, it isn’t covered by the “less than 20 meters” requirement, so it isn’t automatically obligated by that rule to avoid impeding. This makes 20 meters the correct value to complete the statement, because it separates the vessels that must not impede (shorter than 20 m) from those that aren’t governed by this particular provision.