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Which best describes how the law of conservation of energy is obeyed in this closed physical system?



A.
The final mechanical energy of the system is the difference between the original mechanical energy of the system and the change in mechanical energy of the system (ΔE). When the piston does work (W), only the mechanical energy added to the system (Q) is transferred to kinetic energy.


B.
The final thermal energy of the system is the sum of the original internal energy of the system and the change in energy of the system (ΔE). When the piston does work (W), all the thermal energy is transferred to kinetic energy.


C.
The final mechanical energy of the system is the sum of the original internal energy of the system and the change in energy of the system (ΔE). When the piston does work (W), all the mechanical energy is transferred to kinetic energy.


D.
The final thermal energy of the system is the difference between the original internal energy of the system and the change in energy of the system (ΔE). When the piston does work (W), only the thermal energy added to the system (Q) is transferred to kinetic energy.