Question 250Navigation General

The correct answer is D) Group flashing. According to the United States Coast Guard's Aids to Navigation System, an isolated-danger mark is a special-purpose buoy or other navigation aid that indicates an isolated danger such as a wreck or rock. The light phase characteristic of an isolated-danger mark is required to be group flashing, which means the light flashes in groups of two or more flashes, with a longer period of darkness between each group. The other answer choices are incorrect because an interrupted quick flashing light (A) is not the correct characteristic, a long flashing light (B) is not the correct characteristic, and a very quick flashing light (C) is also not the correct characteristic for an isolated-danger mark.