How to you randomly Play a method in a Method Invoker List

I am creating a match the Picture quiz but, I want to randomly select a method ( the method which changes the images and tags) and play it but I don't know how to play it, any suggestions would be much appreciated

   List<MethodInvoker> a = new List<MethodInvoker> { };




 private void frmMarioOtherMatch_Load(object sender, EventArgs e)
        {
  Random randomn = new Random();
            int Questionn = randomn.Next(a.Count);
            a.Add(startmatchleft);
        }