What combination of visual distress signals is effectively approved?

The combination of three handheld red flares and one handheld red flare is effective because it consists of approved visual distress signals that meet U.S. Coast Guard regulations. Handheld red flares are recognized as emergency signaling devices that can be utilized during the day and night and have a high visibility, making them effective for attracting attention in distress situations. The capability of multiple signals in different forms increases the chance of being spotted by nearby vessels or rescuers.

In contrast, while other combinations may have components that could potentially serve as signals, they might not fully comply with the required types or numbers of signals necessary for safe boating practices as stipulated by regulations. For example, relying solely on smoke signals or insufficient quantities may not ensure the same level of visibility during emergencies.