Question 399Navigation General

The correct answer is D) green light. When approaching a lock entrance, the visual signal displayed when a single lock is ready for entrance is a flashing green light. This is in accordance with the United States Aids to Navigation System, which specifies that a flashing green light indicates that the lock is ready for vessel entry. The other answer choices are incorrect because: A) a flashing white light is not used for this purpose, B) a flashing amber light would indicate caution or something else, and C) a flashing red light would indicate that the lock is closed or not ready for entry.