Inheritance - General Questions

Can a struct inherit from a class?

What is the output of the following program?

var c = new C();
Console.WriteLine(c.Describe());
class P { public virtual string Describe() => "P"; }
class C : P { public override string Describe() => base.Describe() + "C"; }

What is the output of the following program?

A obj = new B(); Console.WriteLine(obj.Who());
class A { public string Who() => "A"; }
class B : A { public new string Who() => "B"; }

What is the ultimate base class of all types in C#?

Which method of System.Object returns a string describing the object?