Final answer:
In object-oriented programming, identity is the characteristic that uniquely distinguishes one object from all other objects, akin to a person's unique social security number.
Step-by-step explanation:
In object-oriented programming (OOP), identity refers to the unique property of an object that distinguishes it from all other objects. Even if two objects are of the same class and have the same value for all their attributes (i.e., state), they are considered distinct if they have different identities. Identity in OOP is analogous to how two people can have the same name and birthdate but are distinctly identified by their fingerprints or social security numbers.
Regarding the student's question about what identity is in object-oriented programming, the correct answer is c) It is that which distinguishes an object from all other objects. The other options provided do not directly relate to the concept of identity within OOP. Option a) describes polymorphism, option b) refers to the interface of a class, while option d) describes encapsulation. Identity is crucial in OOP because it allows the system to keep track of each individual object throughout its lifecycle.