If we want to override an abstract method, public abstract void Print(), what is the correct way to declare the method in the derived class?

The virtual keyword is used to modify a method or property declaration, in which case the method or the property is called a virtual member. The implementation of a virtual member can be changed by an overriding member in a derived class.
When a virtual method is invoked, the run-time type of the object is checked for an overriding member. The overriding member in the most derived class is called, which might be the original member, if no derived class has overridden the member.