在ABC三处分别发生几次装箱行为，请说明理由！

Question

static void Main(string[] args){   int a = 5;   object obj = a;  //box   a = 123;Console.WriteLine(a + "," + obj);                //AConsole.WriteLine(a + "," + (int)obj);          //BConsole.WriteLine(a.ToString() + "," + obj);//CConsole.Read(); }