In object oriented programming, which type of data member is shared by all instances of its class rather than having a separate copy in each object?

Introduction / Context:
In many object oriented languages, such as C plus plus, Java, and C sharp, classes can define both instance members and static members. Understanding the difference is important when designing state and behavior. This question asks which type of member is shared by all instances of a class instead of having one copy per object.

Given Data / Assumptions:

• We are working with an object oriented language that supports static members.
• Instance members are allocated separately for each object.
• Static members belong to the class itself, not to any one instance.
• Access modifiers such as public and private control visibility, not sharing semantics by themselves.

Concept / Approach:
A static data member is declared with the static keyword inside a class. Only one copy of a static field exists, regardless of how many objects of the class are created. Every instance and the class itself can refer to this single shared field. This is different from instance fields, which are allocated in each object and hold separate values. Public or private only control who can access a member, not whether it is shared. Therefore, static members are the ones that are shared across instances.

Step-by-Step Solution:
Step 1: Recall that static members are allocated once when the class is loaded or defined, not per instance. Step 2: Understand that instance members exist separately in each object, even if they are public. Step 3: Recognize that inheritance does not make members shared, it simply makes them available in derived classes. Step 4: Compare the answer options and see that option c correctly identifies static members as shared among all instances. Step 5: Reject options that confuse access level, inheritance, or local variables with sharing semantics.

Verification / Alternative check:
In Java, for example, a field declared as static int counter; will hold one value for all objects of that class. Incrementing counter in one method affects the value seen in all other methods and instances. In contrast, a non static field int id; will have a unique value in each object. This behavior directly supports the statement in option c.

Why Other Options Are Wrong:
Option a suggests that public members are shared, but public simply means accessible from outside the class; such members can still be instance specific. Option b describes inheritance, which determines which members are available in derived classes, not whether they are shared at runtime. Option d claims that no member type is shared, contradicting the definition of static. Option e mentions local variables, which live on the stack within a function call and are not shared across objects.

Common Pitfalls:
A frequent mistake is to use static fields to store per user or per request data in web applications, which can lead to unexpected sharing between users. Another pitfall is to mark a field static only to ease access, without considering that its value will be shared. Always ensure that shared state is intentional when using static members.

Final Answer:
The data members shared by all instances of a class are static members, which exist once at the class level, as described in option c.