When using a form-based authentication， which action must be used in the login form？（）

A. the URL pattern that requires authorization
B. the HTTP methods that require authorization
C. the users allowed access to the web resource
D. the J2EE roles allowed access to the web resource
E. the authentication mechanism required by the web resource

A. authorization
B. data integrity
C. confidentiality
D. authentication

A. a base-64 encoded user name and password
B. a form that POSTs to the j_security_check URL
C. an applet that requests the user name and password from the user
D. a hidden field that supplies the login-constraint used by the application