Which of the following is the correct way to call the function abc() of the given class in the following C# code?

class csharp
{
    public int abc(int a)
    {
        Console.WriteLine("A:Just do it!");
        return 0;
    }
}

A.

delegate void del(int a);
csharp s = new csharp();
del d = new del(ref s.abc);
d(10);

B.

csharp s = new csharp();
delegate void d = new del(ref abc);
d(10);

C.

delegate int del(int a);
del d;
csharp s = new csharp();
d = new del(ref s.fun);
d(10);

D. none of the mentioned

Answer: Option C