How to set content type to html and plain text

The mails sent through AWS using below code is normal text format.The mail format should be in html format.Where should one include the option to set content type.Tried Googling but didn't found the answer.

using System;

namespace AmazonSESSample { class Program { static void Main(string[] args) { const String FROM = "SENDER@EXAMPLE.COM"; // Replace with your "From" address. This address must be verified. const String TO = "RECIPIENT@EXAMPLE.COM"; // Replace with a "To" address. If your account is still in the // sandbox, this address must be verified.

        const String SUBJECT = "Amazon SES test (SMTP interface accessed using C#)";
        const String BODY = "This email was sent through the Amazon SES SMTP interface by using C#.";

        // Supply your SMTP credentials below. Note that your SMTP credentials are different from your AWS credentials.
        const String SMTP_USERNAME = "YOUR_SMTP_USERNAME";  // Replace with your SMTP username. 
        const String SMTP_PASSWORD = "YOUR_SMTP_PASSWORD";  // Replace with your SMTP password.

        // Amazon SES SMTP host name. This example uses the us-west-2 region.
        const String HOST = "email-smtp.us-west-2.amazonaws.com";

        // Port we will connect to on the Amazon SES SMTP endpoint. We are choosing port 587 because we will use
        // STARTTLS to encrypt the connection.
        const int PORT = 587;

        // Create an SMTP client with the specified host name and port.
        using (System.Net.Mail.SmtpClient client = new System.Net.Mail.SmtpClient(HOST, PORT))
        {
            // Create a network credential with your SMTP user name and password.
            client.Credentials = new System.Net.NetworkCredential(SMTP_USERNAME, SMTP_PASSWORD);

            // Use SSL when accessing Amazon SES. The SMTP session will begin on an unencrypted connection, and then 
            // the client will issue a STARTTLS command to upgrade to an encrypted connection using SSL.
            client.EnableSsl = true;

            // Send the email. 
            try
            {
                Console.WriteLine("Attempting to send an email through the Amazon SES SMTP interface...");
                client.Send(FROM, TO, SUBJECT, BODY);
                Console.WriteLine("Email sent!");
            }
            catch (Exception ex)
            {
                Console.WriteLine("The email was not sent.");
                Console.WriteLine("Error message: " + ex.Message);
            }
        }

        Console.Write("Press any key to continue...");
        Console.ReadKey();
    }
}

}