Which ONE of the following alternatives is the best to explain why Hot Air Balloons are never launched on hot days but are always launched on cold, clear mornings.

It is too expensive to run the balloon during hot days as the amount of fuel used is triple the amount used on a cold day.
When air temperatures get too high wind gusts form and carry the balloon many kilometres off course.
The cold air provides more of a buoyant force on the balloon than warm air.
The fuel burns better on cold days than on warm, hot days

Which ONE of the following
words has little relevance to
Hot Air Balloons?

Drag
Displacement
Buoyancy
Density