The first law of thermodynamics is a restatement of the law of conservation of:

Solution

1. The first law of thermodynamics states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system, expressed as $\Delta U=Q-W$.
2. This principle dictates that energy cannot be created or destroyed, only transferred or converted between different forms.
3. Because this law accounts for all energy exchanges within a system, it is a direct application of the law of conservation of energy.
4. Hence the answer is (B).