Final answer:
A spontaneous process in a system at constant temperature and pressure is characterized by an increase in the entropy of the universe and a decrease in the Gibbs free energy of the system.
Step-by-step explanation:
A spontaneous process in a system at constant temperature and pressure is characterized by an increase in the entropy of the universe. This means that both the change in entropy of the system (∆Ssys) and the change in entropy of the surroundings (∆Ssurr) must be greater than zero. Therefore, statement I (∆Ssys + ∆Ssurr > 0) is true for a spontaneous process.
The Gibbs free energy (∆G) is a thermodynamic potential that indicates whether a process is spontaneous or nonspontaneous. For a spontaneous process, the change in Gibbs free energy of the system (∆Gsys) must be less than zero. Therefore, statement II (∆Gsys < 0) is also true for a spontaneous process.