txtContent.Text = Regex.Replace(txtContent.Text, @"\bur\b", "your");
txtContent.Text = Regex.Replace(txtContent.Text, @"\bi( |')","I$1");
txtContent.Text = Regex.Replace(txtContent.Text, @"\bi ?m\b","I'm");
txtContent.Text = Regex.Replace(txtContent.Text, @"\bu\b","you");
txtContent.Text = Regex.Replace(txtContent.Text, @"\bur\b", "your");
txtContent.Text = Regex.Replace(txtContent.Text, @"\bcud\b", "could");
txtContent.Text = Regex.Replace(txtContent.Text, @"\bc(o|u)z\b", "because", RegexOptions.IgnoreCase);