Explanation: Marine VHF radios generally operate on low power (1 Watt) for short-range communication to minimize interference. However, using high power (25 Watts) is permissible when necessary for safety or effective communication. * **A) Failure of vessel being called to respond:** If your low-power signal isn't reaching the vessel you're trying to contact, increasing power is a practical and necessary step to establish communication, especially in critical maneuvering situations often associated with Channel 13. * **B) In a blind situation such as rounding a bend in a river:** These are high-risk areas where collision avoidance is paramount. Transmitting high power increases the range and likelihood of your signal being heard by vessels you cannot see, enhancing safety and preventing potential accidents. * **C) During an emergency:** In any emergency, it is crucial to ensure your message is heard as widely and clearly as possible. High power maximizes the reach of your transmission, improving the chances of a timely response. Since all three scenarios represent situations where effective communication is critical for safety and operational necessity, using high power on Channel 13 is justified.