Explanation: A distress message, once initiated, must be repeated until an answer is received from another station or the distress situation is clearly resolved. This practice ensures the highest probability that the critical message will be intercepted and acknowledged. The phrase "especially during the silent periods" refers to established maritime communication procedures where specific times (e.g., the first 3 minutes of every hour and half-hour) were designated for listening for distress calls on certain frequencies. While these specific mandatory silent periods have evolved, the principle of repeating a distress call during quiet times or when listenership is expected remains crucial for increasing the chances of being heard. Options B, C, and D are incorrect because fixed repetition intervals (every 3, 5, or 15 minutes) are not the primary regulatory requirement for repeating distress messages. The overarching rule is to continue transmitting until an acknowledgement is received, making "until an answer is received" the most accurate and comprehensive instruction.