Which of the following provides a wide variety of services?

A.
General purpose servers.

B.
Application servers.

C.
Appliance servers.

D.
Multi-tier servers.

Explanation:
General purpose servers are the most common server products in use and provide multiple services, such email, file, print, and web services that run on an industry-standard network operating system (NOS).
Incorrect Answers:
B: Application servers are configured to run programs that can be accessed by multiple users.
C: Appliance servers provide either a single service, or related services, such as Internet caching and firewall protection.
D: A multi-tiered server structure combines related server types into clusters and can be subdivided into front-end, mid-tier, and back-end servers.
References:
Charles J. Brooks, Server+ Certification Exam Cram 2 (Exam SK0-002), QUE Publishing, Indianapolis, 2006, pp. 8-29.