Question was "Find the largest word in a sentence." I used C# for this.

LongestWord.cs

using System;
using System.Linq;
using System.Text.RegularExpressions;

class MainClass {
  public static string LongestWord(string sen) { 
    // remove unwanted characters (everything except a-z 0-9 or spaces)
    sen = Regex.Replace(sen, @"[^a-zA-Z0-9 ]+", "", RegexOptions.Compiled);
    // split words into array
    string[] words = sen.Split(' ');
    // query for 1 word with largest length
    var final = words.OrderByDescending(s=>s.Length).First();
    return final;
  }

  static void Main() {  
    Console.WriteLine(LongestWord(Console.ReadLine()));
  } 
   
}