Answer :
A. The drop in temperature in a heated room when a window is opened involves the dispersion of thermal energy.
This involves the dispersion of thermal energy from the hot air inside the room to the cooler air outside through conduction and convection.
In thermodynamics, this process is a key example of energy transfer, where thermal energy naturally flows from a region of higher temperature to a region of lower temperature in an attempt to reach thermal equilibrium.
The correct option is A.