For a VFR day flight, what should be entered in block 12?

For a VFR day flight, block 12 is designated for entering the amount of usable fuel on board, expressed in time. This information is critical for flight planning and safety as it informs the pilot and any air traffic control personnel about how long the aircraft can remain in the air based on the fuel available. By specifying the usable fuel in terms of time, it provides a clear metric for assessing whether the airborne duration aligns with the planned route and any contingencies, such as waiting for airport traffic or diverting.

The focus on fuel quantity in time format is particularly important in VFR situations, as it helps ensure that the aircraft not only has enough fuel to complete the journey but also has a safety margin for unforeseen conditions. The other options, while relevant to flight safety and operations, do not align with the specific requirement of block 12 in this context.