a. An object is what classes instantiated are from.
b. An object is an instance of a class.
c. An object is a reference to an attribute.
d. An object is a variable.
Answer:
b. An object is an instance of a class.
Explanation
A class can create objects of itself with different characteristics. So, we can say that an object represents a specific state of the class. This is the reason why objects are called an instance of a class.