C＃没有给出与所需参数相对应的参数

我收到一个错误：没有给出与ReadingMaterial.By（string）所需的形式参数'x'相对应的参数。我正在寻找有关为什么出错的一些指导。我的语法是否错误，或者我还缺少其他内容？我一直在尝试通过使用一些在线教程来学习C＃，并尝试对其进行一些改动。

namespace ReadingMaterials
{
    class Presentation
    {

        static void Main(string[] args)
        {
            aForm Form = new aForm(); // available in hardcopy form aForm.availForm
            Online O = new Online(); // amtBlogs, amtBooks
            Book B = new Book(); // hardCover, softCover
            Magazine M = new Magazine(); // numArticles

            O.blog(5); //contains 5 blogs
            O.oBook(3); //contains 3 online books
            O.By("Beck"); //Written by Beck
            O.words(678); //with 678 combined words
            O.pics(1); // with one pic
            Console.WriteLine("The auther {0} ", O.By());

            Form.availForm();

            B.hardCover(10); //10 hardcover books
            B.softCover(2); //2 softcover books
            B.By("Bruce"); //Writen by Bruce
            B.words(188264); //words combined
            B.pics(15); //15 pictures
            Form.availForm();

            M.articles(5); //5 articles
            M.By("Manddi"); //Writen by Manddi
            M.words(18064);//combined words
            M.pics(81); //81 pictures
            Form.availForm();
        }
    }
    class ReadingMaterial
    {
        protected int amtWords;
        string author;
        protected int pic;
        public void words(int w)
        {
            amtWords = w;

        }
        public void By(string x)
        {
            author = x;

        }
        public void pics(int pi)
        {
            pic = pi;
        }

    }
    class Online : ReadingMaterial
    {
         int amtBlogs;
         int amtBooks;
        public void blog(int s)
        {
            amtBlogs = s;
        }
        public void oBook(int b)
        {
            amtBooks = b;
        }
    }
    class Book : ReadingMaterial
    {
         int hard;
         int soft;
        public void hardCover(int h)
        {
            hard = h;
        }
        public void softCover(int s)
        {
            soft = s;
        }
    }
    class Magazine:ReadingMaterial
    {
         int numArticles;
        public void articles(int a)
        {
            numArticles = a; 
        }

    }
    interface IPrintable
    {
        void availForm();
    }
    class aForm : IPrintable
    {
        public void availForm ()
        {
            Console.WriteLine("Available in hard copy form!");
        }
    }
}