Which equation expresses the first law of thermodynamics, using the convention that work done on the system is positive?

1. A Option A: ΔU = q / w
2. B Option B: ΔU = q − w × T
3. C Option C: ΔH = q × w
4. D Option D: ΔU = q + w

Answer checked 11 October 2026 · How we write and check questions