Which of the following processes of operant conditioning involves the gradual disappearance of a behavior?

a. extinction

b. acquisition

c. shaping

d. discrimination

Among the processes given, extinction is the process of operant conditioning that involves the gradual disappearance of a behavior. The correct option among all the options that are given in the question is the first option or option "a". This process actually leads to gradual weakening and ultimately extinction of the behavior.