Explanation: Bridge-to-bridge transmissions, typically on VHF channels 13 or 67, are generally limited to 1 watt to minimize interference in congested waterways. However, regulations make exceptions for critical situations. **A) When broadcasting a distress message and rounding a bend in a river or traveling in a blind spot.** This is the correct answer because it combines two essential elements: 1. **Distress Message:** Federal Communications Commission (FCC) regulations (47 CFR Part 80.115) specifically authorize the use of maximum power (up to 10 watts for bridge-to-bridge) for distress or emergency communications. 2. **Challenging Propagation:** Rounding a bend or being in a blind spot describes a situation where the normal 1-watt signal might be obstructed, making the higher power necessary to ensure the distress message is received. This practical need for increased power, combined with the critical nature of a distress message, makes it a justified scenario for exceeding 1 watt. **B) When broadcasting a distress message.** While broadcasting a distress message *does* authorize the use of higher power, answer A provides a more complete and practically justified scenario for *why* one would need to exceed the 1-watt limit on a channel typically used for short-range communication. The additional conditions in A highlight when the increased power is truly necessary for the message to be effective. **C) When rounding a bend in a river or traveling in a blind spot.** Simply being in a challenging propagation environment does not, by itself, authorize exceeding the 1-watt limit for routine bridge-to-bridge communications. The communication must be a distress message to justify the higher power. **D) When calling the Coast Guard.** While high power is typically used when calling the Coast Guard, especially on VHF Channel 16, this question specifically asks about "bridge-to-bridge transmission." Calling the Coast Guard is usually done on Channel 16, which has different power usage rules, rather than the dedicated bridge-to-bridge channels (13 or 67) for routine communications between vessels.