.NET Regex and newline

string[] words = new string[] { "ab1", "ab2n", "ab3nn", "ab4r", "ab5rn", "ab6nr" };
Regex regex = new Regex("^[a-z0-9]+$");
foreach (var word in words)
{
    Console.WriteLine("{0} - {1}", word, regex.IsMatch(word));
}

ab1 - True
ab2
 - True
ab3

 - False
 - False
ab5
 - False
ab6
 - False

Regex regex = new Regex(@"^[a-z0-9]+z", RegexOptions.Multiline);

string[] words = new string[] { "ab1", "ab2n", "ab3nn", "ab4r", "ab5rn", "ab6nr" };
Regex regex = new Regex("^[a-z0-9]+$");
foreach (var word in words)
{
    Console.WriteLine("{0} - {1}", word,
        regex.IsMatch(word,"^[a-z0-9]+$",
            System.Text.RegularExpressions.RegexOptions.Singleline |
            System.Text.RegularExpressions.RegexOptions.IgnoreCase |
            System.Text.RegularExpressions.RegexOptions.IgnorePatternWhitespace));
}