using System;

public class Program

{

    public static void Main()

    {

string[] sentences =

{

    "Put the water over there.",

    "They're quite thirsty. Put the blouse",

    "Their water bottles broke."

};

​

//string sPattern = "the(ir)?\\s";

        string sPattern = "Put the *\\s";

​

​

foreach (string s in sentences)

{

    Console.Write($"{s,24}");

​

    if (System.Text.RegularExpressions.Regex.IsMatch(s, sPattern, System.Text.RegularExpressions.RegexOptions.IgnoreCase))

    {

        Console.WriteLine($">>>  (match for '{sPattern}' found)");

    }

    else

    {

        Console.WriteLine("No MATCH");

    }

}   }

}