using System;
using System.Linq;
 
public class Test
{
 
	public static string Extract(string str, string keyword)
    {
 
        string[] arr = str.Split('.');
        string answer = string.Empty;
 
        foreach(string sentence in arr)
        {
            if(sentence.Split(' ').Any(w => w == keyword))
                    answer += sentence+". ";
        }
 
        return answer;
    }
 
	public static void Main()
	{
		string example = "We are living in a yellow submarine. We don't have anything else. Inside the submarine is very tight. So we are drinking all the day. We will move out of it in 5 days.";
 
string keyword = "in";
string answer = Extract(example, keyword);
Console.WriteLine(answer);
	}
}

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