Almost only letters

Given a string, write a method that checks if consists of letters only and ends with period. If string has more than one word, words are separated by space.
Expected input and output
AlmostOnlyLetters("She is nice.") → true AlmostOnlyLetters("true 222.") → false
using System;
using System.Text.RegularExpressions;

namespace CSharpExercises.Exercises.Regular_expressions
{
    class AlmostOnlyLettersTask
    {
        public static bool AlmostOnlyLetters(string word)
        {
            Regex regex = new Regex(@"^[A-Za-z\s]+\.$");
            Match match = regex.Match(word);

            return match.Success;
        }

        public static void Main()
        {
            Console.WriteLine(AlmostOnlyLetters("Very hot."));      // True
            Console.WriteLine(AlmostOnlyLetters("full of hope"));   // False
            Console.WriteLine(AlmostOnlyLetters(""));               // False
            Console.WriteLine(AlmostOnlyLetters("short."));         // True
        }
    }
}