Routers are switching devices that operate at the network layer (layer 3) by examining network addresses.
Source: 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 111).

Section: Network and Telecommunications
Explanation/Reference:
A common way to create fault tolerance with leased lines is to group several T1s together with an inverse multiplexer placed at both ends of the connection.
In fact it would be a Multiplexer at one end and DeMultiplexer at other end or vice versa. Inverse Multiplexer at both end.
In electronics, a multiplexer (or mux) is a device that selects one of several analog or digital input signals and forwards the selected input into a single line. A multiplexer of 2n inputs has n select lines, which are used to select which input line to send to the output. Multiplexers are mainly used to increase the amount of data that can be sent over the network within a certain amount of time and bandwidth. A multiplexer is also called a data selector.
An electronic multiplexer makes it possible for several signals to share one device or resource, for example one A/D converter or one communication line, instead of having one device per input signal.
On the other hand, a demultiplexer (or demux) is a device taking a single input signal and selecting one of many data-output-lines, which is connected to the single input. A multiplexer is often used with a complementary demultiplexer on the receiving end.
An electronic multiplexer can be considered as a multiple-input, single-output switch, and a demultiplexer as a single-input, multiple-output switch References:
KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 72.
and
https://secure.wikimedia.org/wikipedia/en/wiki/Multiplexer

Section: Risk, Response and Recovery
Explanation/Reference:
The recovery point objective (RPO) is the maximum acceptable level of data loss following an unplanned
"event", like a disaster (natural or man-made), act of crime or terrorism, or any other business or technical disruption that could cause such data loss. The RPO represents the point in time, prior to such an event or incident, to which lost data can be recovered (given the most recent backup copy of the data).
The recovery time objective (RTO) is a period of time within which business and / or technology capabilities must be restored following an unplanned event or disaster. The RTO is a function of the extent to which the interruption disrupts normal operations and the amount of revenue lost per unit of time as a result of the disaster.
These factors in turn depend on the affected equipment and application(s). Both of these numbers represent key targets that are set by key businesses during business continuity and disaster recovery planning; these targets in turn drive the technology and implementation choices for business resumption services, backup / recovery / archival services, and recovery facilities and procedures.
Many organizations put the cart before the horse in selecting and deploying technologies before understanding the business needs as expressed in RPO and RTO; IT departments later bear the brunt of user complaints that their service expectations are not being met. Defining the RPO and RTO can avoid that pitfall, and in doing so can also make for a compelling business case for recovery technology spending and staffing.
For the CISSP candidate studying for the exam, there are no such objectives for "point of time," and "critical time." Those two answers are simply detracters.
Reference:
http://www.wikibon.org/Recovery_point_objective_/_recovery_time_objective_strategy

The main characteristic of a multi-homed host is that is has multiple network interfaces, each connected to logically and physically separate networks. IP routing should be disabled to prevent the firewall from routing packets directly from one interface to the other.
Source: FERREL, Robert G, Questions and Answers for the CISSP Exam, domain 2 (derived from the Information Security Management Handbook, 4th Ed., by Tipton & Krause).

Explanation/Reference:
In addition to the accuracy of the biometric systems, there are other factors that must also be considered.
These factors include the enrollment time, the throughput rate, and acceptability.
Enrollment time is the time it takes to initially "register" with a system by providing samples of the biometric characteristic to be evaluated. An acceptable enrollment time is around two minutes.
For example, in fingerprint systems, the actual fingerprint is stored and requires approximately 250kb per finger for a high quality image. This level of information is required for one-to-many searches in forensics applications on very large databases.
In finger-scan technology, a full fingerprint is not stored-the features extracted from this fingerprint are stored using a small template that requires approximately 500 to 1000 bytes of storage. The original fingerprint cannot be reconstructed from this template.
Updates of the enrollment information may be required because some biometric characteristics, such as voice and signature, may change with time.
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 37 & 38.