The primary reason to perform a risk assessment is to determine the current risk profile of the organization, which is the level of risk exposure and the likelihood and impact of potential threats. This will help the organization to identify and prioritize the risks that need to be addressed and to align the risk management strategy with the business objectives. A risk assessment may also help to achieve compliance, support the BIA, and allocate budget, but these are not the primary reasons. References: ISACA Glossary of Terms, section
"risk assessment"

Section: Protection of Information Assets
Explanation:
Historically, the waterfall model has been best suited to the stable conditions described in choice
A. When the degree of uncertainty of the system to be delivered and the conditions in which it will be used
rises, the waterfall model has not been successful, in these circumstances, the various forms of iterative
development life cycle gives the advantage of breaking down the scope of the overall system to be
delivered, making the requirements gathering and design activities more manageable. The ability to deliver
working software earlier also acts to alleviate uncertainty and may allow an earlier realization of benefits.
The choice of a design and programming approach is not itself a determining factor of the type of software
development life cycle that is appropriate. The use of new technology in a project introduces a significant
element of risk. An iterative form of development, particularly one of the agile methods that focuses on
early development of actual working software, is likely to be the better option to manage this uncertainty.

Explanation/Reference:
Mainframe computer is a large, general purpose computer that are made to share their processing power and facilities with thousands of internal or external users. The term mainframe computer was created to distinguish the traditional, large, institutional computer intended to service multiple users from the smaller, single user machines. These computers are capable of handling and processing very large amounts of data quickly. Mainframe computers are used in large institutions such as government, banks and large corporations. They are measured in MIPS (million instructions per second) and respond to up to 100s of millions of users at a time.
For your exam you should know the information below:
Common Types of computers
Supercomputers
A supercomputer is focused on performing tasks involving intense numerical calculations such as weather forecasting, fluid dynamics, nuclear simulations, theoretical astrophysics, and complex scientific computations. A supercomputer is a computer that is at the frontline of current processing capacity, particularly speed of calculation. The term supercomputer itself is rather fluid, and the speed of today's supercomputers tends to become typical of tomorrow's ordinary computer. Supercomputer processing speeds are measured in floating point operations per second, or FLOPS. An example of a floating point operation is the calculation of mathematical equations in real numbers. In terms of computational capability, memory size and speed, I/O technology, and topological issues such as bandwidth and latency, supercomputers are the most powerful, are very expensive, and not cost-effective just to perform batch or transaction processing. Transaction processing is handled by less powerful computers such as server computers or mainframes.
Mainframes
The term mainframe computer was created to distinguish the traditional, large, institutional computer intended to service multiple users from the smaller, single user machines. These computers are capable of handling and processing very large amounts of data quickly. Mainframe computers are used in large institutions such as government, banks and large corporations. They are measured in MIPS (million instructions per second) and respond to up to 100s of millions of users at a time.
Mid-range servers
Midrange systems are primarily high-end network servers and other types of servers that can handle the large-scale processing of many business applications. Although not as powerful as mainframe computers, they are less costly to buy, operate, and maintain than mainframe systems and thus meet the computing needs of many organizations. Midrange systems have become popular as powerful network servers to help manage large Internet Web sites, corporate intranets and extranets, and other networks. Today, midrange systems include servers used in industrial process-control and manufacturing plants and play major roles in computer-aided manufacturing (CAM). They can also take the form of powerful technical workstations for computer-aided design (CAD) and other computation and graphics-intensive applications.
Midrange system are also used as front-end servers to assist mainframe computers in telecommunications processing and network management.
Personal computers
A personal computer (PC) is a general-purpose computer, whose size, capabilities and original sale price makes it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator. This contrasted with the batch processing or time-sharing models which allowed larger, more expensive minicomputer and mainframe systems to be used by many people, usually at the same time. Large data processing systems require a full-time staff to operate efficiently.
Laptop computers
A laptop is a portable personal computer with a clamshell form factor, suitable for mobile use.[1] They are also sometimes called notebook computers or notebooks. Laptops are commonly used in a variety of settings, including work, education, and personal multimedia.
A laptop combines the components and inputs as a desktop computer; including display, speakers, keyboard, and pointing device (such as a touchpad), into a single device. Most modern-day laptop computers also have a webcam and a mice (microphone) pre-installed. [citation needed] A laptop can be powered either from a rechargeable battery, or by mains electricity via an AC adapter. Laptops are a diverse category of devices, and other more specific terms, such as ultra-books or net books, refer to specialist types of laptop which have been optimized for certain uses. Hardware specifications change vastly between these classifications, forgoing greater and greater degrees of processing power to reduce heat emissions.
Smartphone, tablets and other handheld devices
A mobile device (also known as a handheld computer or simply handheld) is a small, handheld computing device, typically having a display screen with touch input and/or a miniature keyboard.
A handheld computing device has an operating system (OS), and can run various types of application software, known as apps. Most handheld devices can also be equipped with Wi-Fi, Bluetooth, and GPS capabilities that can allow connections to the Internet and other Bluetooth-capable devices, such as an automobile or a microphone headset. A camera or media player feature for video or music files can also be typically found on these devices along with a stable battery power source such as a lithium battery.
Early pocket-sized devices were joined in the late 2000s by larger but otherwise similar tablet computers.
Much like in a personal digital assistant (PDA), the input and output of modern mobile devices are often combined into a touch-screen interface.
Smartphone's and PDAs are popular amongst those who wish to use some of the powers of a conventional computer in environments where carrying one would not be practical. Enterprise digital assistants can further extend the available functionality for the business user by offering integrated data capture devices like barcode, RFID and smart card readers.
Thin Client computers
A thin client (sometimes also called a lean, zero or slim client) is a computer or a computer program that depends heavily on some other computer (its server) to fulfill its computational roles. This is different from the traditional fat client, which is a computer designed to take on these roles by itself. The specific roles assumed by the server may vary, from providing data persistence (for example, for diskless nodes) to actual information processing on the client's behalf.
The following answers are incorrect:
Mid-range servers- Midrange systems are primarily high-end network servers and other types of servers that can handle the large-scale processing of many business applications. Although not as powerful as mainframe computers, they are less costly to buy, operate, and maintain than mainframe systems and thus meet the computing needs of many organizations. Midrange systems have become popular as powerful network servers to help manage large Internet Web sites, corporate intranets and extranets, and other networks. Today, midrange systems include servers used in industrial process-control and manufacturing plants and play major roles in computer-aided manufacturing (CAM).
Personal computers - A personal computer (PC) is a general-purpose computer, whose size, capabilities and original sale price makes it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator. This contrasted with the batch processing or time-sharing models which allowed larger, more expensive minicomputer and mainframe systems to be used by many people, usually at the same time. Large data processing systems require a full-time staff to operate efficiently.
Thin Client computers- A thin client (sometimes also called a lean, zero or slim client) is a computer or a computer program that depends heavily on some other computer (its server) to fulfill its computational roles. This is different from the traditional fat client, which is a computer designed to take on these roles by itself. The specific roles assumed by the server may vary, from providing data persistence (for example, for diskless nodes) to actual information processing on the client's behalf.
The following reference(s) were/was used to create this question:
CISA review manual 2014 page number 246
http://en.wikipedia.org/wiki/Thin_client
http://en.wikipedia.org/wiki/Mobile_device
http://en.wikipedia.org/wiki/Personal_computer
http://en.wikipedia.org/wiki/Classes_of_computers
http://en.wikipedia.org/wiki/Laptop

Explanation/Reference:
Explanation:
A VPN hides information from sniffers on the net using encryption. It works based on tunneling. A VPN does not analyze information packets and, therefore, cannot enforce security policies, it also does not check the content of packets, so it cannot detect misuse or mistakes. A VPN also does not perform an authentication function and, therefore, cannot regulate access.