What will be the output of the following C# code?

static void Main(string[] args)
{
    char ch = Convert.ToChar('a' | 'b' | 'c');
    switch (ch)
    {
    case 'A':
    case 'a':
        Console.WriteLine("case A|case a");
        break;
    case 'B':
    case 'b':
        Console.WriteLine("case B|case b");
        break;
    case 'C':
    case 'c':
    case 'D':
    case 'd':
        Console.WriteLine("case D|case d");
        break;
    }
    Console.ReadLine();
}

A. Compile time error

B. case A|case a

C. case B|case b

D. case D|case d

Answer: Option D