Use of hot air ballon in meteorological observatory is an application of :

Use of hot air balloon in sports and metorological observation is an application of

Use of hot air ballons in sports and meteorological observations in an application of

Use of hot air ballons in sports and meteorological observations in an application of

Assertion : The use of hot air balloons in sports and for meteorological observations is an application of Charle's law Reason : Hot air is less and hence gases expand on heating