这个c#题目是训练了什么?谁知道? 开源的!

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace sj4
{
    class Program
    {
        static void Main(string[] args)
        {
            bus b1 = new bus("红色", "高雅巴士", 20);
            bus b2 = new bus("蓝色", "高雅巴士", 10);
            bus b3 = new bus("绿色", "高雅巴士", 30);

            truck t1 = new truck("黄色", 30, "大象");
            truck t2 = new truck("绿色", 25, "大象");
            truck t3 = new truck("金色", 20, "大象");

            mini_truck mt1 = new mini_truck("金色", 10, "小象");
            mini_truck mt2 = new mini_truck("红色", 10, "小象");
            List<vehicle> vehicleBox = new List<vehicle>();
            vehicleBox.Add(b1);
            vehicleBox.Add(b2);
            vehicleBox.Add(b3);
            vehicleBox.Add(t1);
            vehicleBox.Add(t2);
            vehicleBox.Add(t3);
            vehicleBox.Add(mt1);
            vehicleBox.Add(mt2);
            for (int i = 0; i < vehicleBox.Count; i++)
            {
                if (vehicleBox[i] is bus)
                {
                    bus b = (bus)(vehicleBox[i]);
                    b.Run();
                }
                if (vehicleBox[i] is truck)
                {
                    truck t = (truck)(vehicleBox[i]);
                    t.Run();
                }
                if (vehicleBox[i] is mini_truck)
                {
                    mini_truck mt = (mini_truck)(vehicleBox[i]);
                    mt.Run();
                }
            }
        }
    }
    class bus:vehicle
    {
        public bus() { }

        public bus(string color,string name,int passengernum): base(color,name,passengernum)
        {
            ;
        }
        public override void Run()
        {
            string mes = string.Format("{0}颜色的{1}公共汽车,乘客{2}名",base.Color,base.Name,base.Passengernum);
            Console.WriteLine(mes);
        }
    }
    class truck:vehicle
    {
        public truck() { }

        public truck(string color, int load, string name): base(color,load,name)
        {
            ;
        }
        public override void Run()
        {
            string mes = string.Format("{0}颜色的{1}货车,载重{2}吨",base.Color,base.Name,base.Load);
            Console.WriteLine(mes);
        }
    }

    class mini_truck:truck
    {
        public mini_truck() { }

        public mini_truck(string color, int load, string name): base(color,load,name)
        {
            ;
        }
        public void Run()
        {
            string mes = string.Format("{0}颜色的{1}小货车,载重{2}吨", base.Color, base.Name, base.Load);
            Console.WriteLine(mes);
        }
    }

    /// <summary>
    /// 交通工具爹类
    /// </summary>
   abstract class vehicle
    {
        public vehicle() { }

        public vehicle(string color, string name, int passengernum)
        {
            this.color = color;
            this.name = name;
            this.passengernum = passengernum;

        }
        public vehicle(string color,int load,string name)
        {
            this.color = color;
            this.name = name;
            this.load = load;
        }
        private string color;
        private string name;
        private int passengernum;
        private int load;

        public int Load
        {
            get { return load; }
            set { load = value; }
        }

        public int Passengernum
        {
            get { return passengernum; }
            set { passengernum = value; }
        }

        public string Name
        {
            get { return name; }
            set { name = value; }
        }
     
        public string Color
        {
            get { return color; }
            set { color = value; }
        }
 

        public abstract void Run();
       
    }
}

继承的传递性和到底调用的哪个方法。