To answer this question, we need to understand the concept of instance variables in object-oriented programming.

An instance variable represents an attribute of an object. It is a variable that is unique to each instance (or object) of a class. It holds data that is specific to that particular object.

Now let's go through each option and explain why it is right or wrong:

A. represents an attribute of an object: This option is correct. As explained above, an instance variable represents an attribute of an object. It holds data that is specific to that particular object.

B. is an object of a class: This option is incorrect. An instance variable is not an object itself, but rather a variable that is associated with an object.

C. is a method of a class: This option is incorrect. An instance variable is not a method. Methods are actions or behaviors that objects can perform, while instance variables hold data or state of an object.

D. a and c: This option is incorrect. As explained above, an instance variable represents an attribute of an object, but it is not a method of a class. Therefore, the correct answer is not D.

The correct answer is: A