Explanation/Reference:
Distributed computing provides a scalable runtime platform capable of handling many concurrent users by allowing related components to be spread out but at the same time enabling them to work in unison. It allows applications to be broken down into smaller, modular components and be deployed across a distributed infrastructure that leverages the power and flexibility of networked servers. Layered architecture enables separation of concern by defining individual logical layers that can be deployed independently, taking advantage of the distributed infrastructure.
Distributed architectures allow selective scalability of the layers that require more capacity to handle the load. This allows efficient use of the hardware and software resources and optimization of performance by fine-tuning the appropriate layer or component. In contrast to some of the other models, distributed computing generally is a CAPEX model where the distributed infrastructure is built in-house for applications to be deployed.
Note: In distributed computing a program is split up into parts that run simultaneously on multiple computers communicating over a network. Distributed computing is a form of parallel computing, but parallel computing is most commonly used to describe program parts running simultaneously on multiple processors in the same computer.
Both types of processing require dividing a program into parts that can run simultaneously, but distributed programs often must deal with heterogeneous environments, network links of varying latencies, and unpredictable failures in the network or the computers.
Note 2: Distributed computing allows multiple, autonomous computers to work in concert to solve a problem or provide a business solution. Distributed computing is used in the vast majority of modern enterprise business solutions.
Incorrect answers:
D: Latency could increase. The network speeds have improved by an order of magnitude in the recent years, yet the network latency can not be ignored. In tiered architectures, there is a cost involved in distributing "too much".
Reference: Oracle Reference Architecture, Application Infrastructure Foundation, Release 3.0