Explanation: The getUserPrincipal() method determines the principle name of the current user and returns the java.security.Principal object. The java.security.Principal object contains the remote user name. The value of the getUserPrincipal () method returns null if no user is authenticated. Answer: C is incorrect. The getRemoteUser() method returns the user name that is used for the client authentication. The value of the getRemoteUser() method returns null if no user is authenticated. Answer: B is incorrect. The isUserInRole() method determines whether the remote user is granted a specified user role. The value of the isUserInRole() method returns true if the remote user is granted the specified user role; otherwise it returns false. Answer: D is incorrect. The getCallerPrincipal() method is used to identify a caller using a java.security.Principal object. It is not used in the HttpServletRequest interface.