7. Which of the following is the 1st law of thermodynamics? (A) The entropy of the a system undergoing a spontaneous process must decrease. (B) The heat of an open system must remain constant throughout the entirety of the process. (C) A process’s change in Gibbs free energy can determine the process’s spontaneity. (D) The change in a system’s internal energy is equal to the sum of heat added into the system and the work done by the system.