Explanation/Reference:
Virtual Private Networks allow a trusted network to communicate with another trusted network over untrusted networks such as the Internet.
Screened Subnet: A screened subnet is essentially the same as the screened host architecture, but adds an extra strata of security by creating a network which the bastion host resides (often call perimeter network) which is separated from the internal network. A screened subnet will be deployed by adding a perimeter network in order to separate the internal network from the external. This assures that if there is a successful attack on the bastion host, the attacker is restricted to the perimeter network by the screening router that is connected between the internal and perimeter network.
Digital Certificates: Digital Certificates will be used in the intitial steps of establishing a VPN but they would not provide the encryption and integrity by themselves.
Encryption: Even thou this seems like a choice that would include the other choices, encryption by itself does not provide integrity mechanims. So encryption would satisfy only half of the requirements of the question.
Source: TIPTON, Harold F & KRAUSE, Micki, Information Security Management Handbook, 4th edition (volume 1), 2000, CRC Press, Chapter 3, Secured Connections to External Networks (page 65).

Explanation/Reference:
The Pretty Good Privacy (PGP) email encryption system was developed by Phil Zimmerman. For encrypting messages, it actually uses AES with up to 256-bit keys, CAST, TripleDES, IDEA and Twofish.
RSA is also used in PGP, but only for symmetric key exchange and for digital signatures, but not for encryption.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 4: Cryptography (pages 154, 169).
More info on PGP can be found on their site at http://www.pgp.com/display.php?pageID=29.

Port 119 is normally used for the Network News Transfer Protocol. It is thus
not need for a mail server, which would normally listen to ports 25 (SMTP), 110 (POP3)
and 143 (IMAP).
Source: STREBE, Matthew and PERKINS, Charles, Firewalls 24seven, Sybex 2000,
Chapter 1: Understanding Firewalls.

Section: Risk, Response and Recovery
Explanation/Reference:
This step is not a part of RISK ANALYSIS.
A risk analysis has three main goals: identify risks, quantify the impact of potential threats, and provide an economic balance between the impact of the risk and the cost of the associated countermeasure. Choosing the best countermeasure is not part of the risk analysis.
Source: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, chapter 3:
Security Management Practices (page 73).
HARRIS, Shon, Mike Meyers' CISSP(R) Certification Passport, 2002, McGraw-Hill, page 12.

Section: Security Operation Adimnistration
Explanation/Reference:
It is considered to be a technical control.
Logical is synonymous with Technical Control. That was the easy answer.
There are three broad categories of access control: Administrative, Technical, and Physical.
Each category has different access control mechanisms that can be carried out manually or automatically. All of these access control mechanisms should work in concert with each other to protect an infrastructure and its data.
Each category of access control has several components that fall within it, as shown here:
Administrative Controls
* Policy and procedures
* Personnel controls
* Supervisory structure
* Security-awareness training
* Testing
Physical Controls
Network segregation
Perimeter security
Computer controls
Work area separation
Data backups
Technical Controls
System access
Network architecture
Network access
Encryption and protocols
Control zone
Auditing
The following answers are incorrect :
Screening of personnel is considered to be an administrative control
Development of policies, standards, procedures and guidelines is considered to be an administrative control Change control procedures is considered to be an administrative control.
Reference : Shon Harris AIO v3 , Chapter - 3 : Security Management Practices , Page : 52-54