Explanation: User data constraint is a security constraint element summarized in the Java Servlet Specification 2.4. It sets up a requirement to receive the constrained requests over a protected layer connection, such as TLS (Transport Layer Security). The user data constraint offers guarantee (NONE, INTEGRAL, and CONFEDENTIAL) for the transportation of data between client and server. If a request does not have user data constraint, the container accepts the request after it is received on a connection. Answer: C is incorrect. Web resource collection is a set of URL patterns and HTTP operations that define all resources required to be protected. It is a security constraint element summarized in the Java Servlet Specification v2.4. The Web resource collection includes the following elements: URL patterns HTTP methods Answer: B is incorrect. Authorization constraint is a security constraint element summarized in the Java Servlet Specification 2.4. It sets up a requirement for authentication and names the authorization roles that can access the URL patterns and HTTP methods as defined by the security constraint. In the absence of a security constraint, the container accepts the request without requiring any user authentication. If no authorization role is specified in the authorization constraint, the container cannot access constrained requests. The wildcard character “*” specifies all authorization role names that are defined in the deployment descriptor. Answer: D is incorrect. It is not a security constraint element.