.NET platform does not support multiple inheritance. Do not confuse multilevel inheritance with multiple inheritance. With multiple inheritance we can have a subclass that inherits from two classes at the same time.
C# Inheritance for Java Programmers
So what is a class? A class is a plan or a blueprint for an object, like a blueprint for a house. What if you want your house to look like a neighbor’s house? Well, you change the blueprint and add another fireplace.