Error is not all code paths return a value

namespace WorkList
{
    public class Stud_Information
    {
        public List<string> students= new List<string>();

        public static string Stud()
        {
            List<string> students = new List<string>();
            students.Add("Mary");
        }        
    }
}

namespace WorkList
{
    class Program
    {

        static void Main(string[] args)
        {
           Stud_Information.Stud();
            for (var i = 0; i < students.Count; i++)
            {
                Console.WriteLine("[" + i.ToString() + "] " + students[i] );
            }
            Console.ReadKey();
}

}