As you know, multiple class inheritance is not possible in C#. But you can achieve this goal using interfaces because multiple interface inheritance is allowed in C#. We can learn this thing better with an example.
Create 2 interfaces IA and IB. IA contains a method PrintA() and IB contains a method PrintB(). Create 3 classes A, B, and C. Class A and B inheriting from interfaces IA and IB respectively. Class C is inheriting from interfaces IA and IB. As per condition, class A and B must provide implementation for their respective interface members. Same goes for class C, but with a little twist. In class C, we will create instances of class A and class B. Then, we will create 2 methods PrintA() and PrintB(). Because we have instantiated class A and B, we have access to their methods. We will call those methods using PrintA() and PrintB() methods available in class C.
This is a bit of work, which will give you access to methods available in both the classes A and B by creating an instance of class C.