Explanation/Reference:
Explanation:
The main protocols that make up the IPSec suite and their basic functionality are as follows:
Authentication Header (AH) provides data integrity, data origin authentication, and protection from

replay attacks.
Encapsulating Security Payload (ESP) provides confidentiality, data-origin authentication, and data

integrity.
Internet Security Association and Key Management Protocol (ISAKMP) provides a framework for

security association creation and key exchange.
Internet Key Exchange (IKE) provides authenticated keying material for use with ISAKMP

Incorrect Answers:
B: The IPsec protocol uses Encapsulating Security Payload (ESP) for encryption, not IKE.
C: The IPSec protocol uses data signatures to provide data integrity. IKE is not used for signing the data packets.
D: The IPsec protocol does not enforce quality of service.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 705

Bastion Host: A system that has been hardened to resist attack at some critical point of entry, and which is installed on a network in such a way that it is expected to come under attack. Bastion hosts are often components of firewalls, or may be 'outside" Web servers or public access systems. Generally, a bastion host is running some form of general purpose operating system (e.g., LNIX, VMS, WNT, etC.) rather than a ROM-based or firmware operating system. http://www.securesynergy.com/library/articles/it_glossary/glossary_b.php

As session key is a symmetric key that is used to encrypt messages between two users. A session key is only good for one communication session between users.
For example , If Tanya has a symmetric key that she uses to encrypt messages between
Lance and herself all the time , then this symmetric key would not be regenerated or changed. They would use the same key every time they communicated using encryption.
However , using the same key repeatedly increases the chances of the key being captured and the secure communication being compromised. If , on the other hand , a new symmetric key were generated each time Lance and Tanya wanted to communicate , it would be used only during their dialog and then destroyed. if they wanted to communicate and hour later , a new session key would be created and shared.
The other answers are not correct because :
Public Key can be known to anyone.
Private Key must be known and used only by the owner.
Secret Keys are also called as Symmetric Keys, because this type of encryption relies on each user to keep the key a secret and properly protected.
REFERENCES:
SHON HARRIS , ALL IN ONE THIRD EDITION : Chapter 8 : Cryptography , Page : 619-
620