using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        List<string> list1 = new List<string>()

        {"A"};

        List<string> list2 = new List<string>()

        {"B", "C"};

        List<string> list3 = new List<string>()

        {"D", "E", "F"};

        string temp = "";

        foreach (var item1 in list1)

        {

            foreach (var item2 in list2)

            {

                foreach (var item3 in list3)

                {

                    temp += ($"'{item1}','{item2}','{item3}';");

                }

            }

        }

​

        temp.Dump();

    }

}