Which combination of VDS signals is recognized for both day and night use?

The combination of three handheld red flares is recognized for both day and night use as an effective visual distress signal (VDS). These flares emit a bright red light that is easily visible, making them suitable for signaling in various conditions and times of day, including darkness. Red flares are universally accepted as a standard for emergency signaling at sea and are visible from long distances.

The other options include variations of signals that might not be as effective or universally recognized. For instance, while handheld orange smoke signals can be useful during the day, they are not effective at night. Similarly, a combination of a red flare and orange smoke may not meet the requirements for both day and night visibility. Lastly, although an electric light can be effective at night, it does not serve the purpose of signaling during the day as effectively as the bright red flares do. Hence, the three handheld red flares serve as the best choice for a combination that ensures visibility and compliance with safety regulations at all times.