The correct answer is B) they can be used by mariners who do not know Morse code. The key advantage of NAVTEX radio warnings is that they can be received and understood by mariners without any specialized knowledge, such as the ability to interpret Morse code. NAVTEX broadcasts maritime safety information in a simple, digital format that can be displayed on a dedicated receiver, eliminating the need for Morse code reception and interpretation. This makes NAVTEX an accessible and user-friendly source of critical navigational and weather warnings for a wide range of mariners. The other answer choices are incorrect because they do not accurately capture the primary benefit of NAVTEX. Option A is incorrect as NAVTEX does not necessarily cover a broad spectrum of the radio band. Option C is incorrect as NAVTEX information is not only broadcast at specified times. Option D is incorrect as a dedicated NAVTEX receiver, not an ordinary FM radio, is required to receive these warnings.