How should the developer design the Apex classes?

A developer created a Lightning component to display a short text summary for an object and wants to use it with multiple Apex classes.

How should the developer design the Apex classes?
A . Have each class define method getObject() that returns the sObject that is controlled by the Apex class.
B . Extend each class from the same base class that has a method getTextSummary() that returns the summary.
C . Have each class implement an interface that defines method getTextSummary() that returns the summary.
D . Have each class define method getTextSummary() that returns the summary.

Answer: C