What Am I Doing Wrong?

using System;

class Program
{

    static string CheckSpeed(double speed)
    {
        if(speed > 65)
        {
            Console.WriteLine("too fast");
         }
        else if(speed < 45)
        {
            Console.WriteLine("too slow");
         }
        else
        {
            Console.WriteLine("speed OK");
         }
        return  speed;

    }

    static void Main(string[] args)
    {
        // This should print "too slow".
        Console.WriteLine(CheckSpeed(44));
        // This should print "too fast".
        Console.WriteLine(CheckSpeed(88));
        // This should print "speed OK".
        Console.WriteLine(CheckSpeed(55));
    }

}