The correct answer is "Strong * (star) Property".
* Answer "the Discretionary Security Property" specifies discretionary access control in the
Bell-LaPadula model by the use of an access matrix.
* Answer "Simple * (star) Property" is distracter.
* Answer "* (star) Security Property", in the Bell-LaPadula model, states, The writing of information by a subject at a higher level of sensitivity to an object at a lower level of sensitively is not permitted (no write down).

The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private Internets - 10.0.0.0 to 10.255.255.255, 172.16.0.0 to 172.31.255.255, and 192.168.0.0 to 192.168.255.255- that are known as "global non-routable addresses."" Pg. 94 Krutz: The CISSP Prep Guide.

PPTP operates at the data link layer (layer 2) of the OSI model and uses native PPP authentication and encryption services. Designed for individual client to server connections, it enables only a single point-to-point connection per session. PPTP - Point-to-Point Tunneling Protocol - extends the Point to Point Protocol (PPP) standard for traditional dial-up networking. PPTP is best suited for the remote access applications of VPNs, but it also supports LAN internetworking.
PPTP operates at Layer 2 of the OSI model. Using PPTP PPTP packages data within PPP packets, then encapsulates the PPP packets within IP packets (datagrams) for transmission through an Internet-based VPN tunnel. PPTP supports data encryption and compression of these packets. PPTP also uses a form of General Routing Encapsulation (GRE) to get data to and from its final destination.
Reference(s) used for this question: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 3: Telecommunications and Network Security (page 95). and http://compnetworking.about.com/od/vpn/l/aa030103a.htm
and http://technet.microsoft.com/en-us/library/cc768084.aspx

Layer 7 Applications Layer Provides specific services for applications such as:
FTP (File Transfer Protocol)
TFTP (Trivial File Transfer Protocol)Used by some X-Terminal systems
HTTP (Hypertext Transfer Protocol)
SNMP (Simple Network Management Protocol Helps network managers locate and correct problems in a TCP/IP network
Used to gain information from network devices such as count of packets received and routing tables
SMTP (Simple Mail Transfer Protocol)Used by many email applications.
Source: STEINER, Kurt, Telecommunications and Network Security, Version 1, May 2002,
CISSP Open Study Group (Domain Leader: skottikus), Page 12.

The original Answer was B.
This is incorrect as cipthertext is the result not an
authentication code.
"If meaningful plaintext is not automatically recognizable, a message authentication code (MAC)
can be computed and appended to the message. The computation is a function of the entire message and a secret key; it is practically impossible to find another message with the same authenticator. The receiver checks the authenticity of the message by computing the MAC using the same secret key and then verifying that the computed value is the same as the one transmitted with the message. A MAC can be used to provide authenticity for unencrypted messages as well as for encrypted ones. The National Institute of Standards and Technology (NIST) has adopted a standard for computing a MAC. (It is found in Computer Data Authentication, Federal Information Processing Standards Publication (FIPS PUB) 113.)" http://www.cccure.org/Documents/HISM/637-639.html from the Handbook of Information Security Management by Micki Krause