Which of the following gas laws explains the application of hot air balloons in sports and meteorological observations?

The correct option is A Charles' law
Charles' law states that, at constant pressure, the volume of a gas is directly related to the temperature of that gas in Kelvin scale.
In case of a hot air balloon, upon ignition of the fuel, the temperature of the air inside the balloon is increased. As a result, the volume of the gas increases (in accordance with Charles' law). When the air inside the balloon expands, it becomes less dense and provides the lift for the hot air balloon.