Consider an infinitesimally small fluid element moving along with the flow. Apply the first law of thermodynamics to this model. Which of these statements is correct?

• A. The rate of change of the total energy is equal to the rate of heat addition and work extraction
• B. The rate of work extraction is equal to the rate of heat addition and the rate of change of the total energy
• C. The rate of heat addition is equal to the rate of work extraction and the rate of change of the total energy
• D. The rate of change of the total energy is equal to the rate of work extraction