Final answer:
The term 'server farm' refers to a collection of servers. It is a system that consists of numerous servers housed in data centers to provide extensive server functionality. Other terms such as server database, portal, and data server have different meanings and should not be confused with a server farm.
Step-by-step explanation:
The term that refers to a collection of servers is B) server farm. A server farm or server cluster is a group of computer servers usually maintained by an organization to supply server functionality far beyond the capability of a single machine. Server farms often consist of thousands of computers which require a large amount of power to run and are typically housed in data centers which are equipped with redundant power supplies, networking connections, and HVAC systems.
A server database is more accurately a database server, which is a server that uses a database application that provides database services to other computer programs or computers. As for a portal, this is a web-based platform that collects information from different sources into a single user interface and presents users with the most relevant information for their context. Lastly, a data server generally refers to a server that provides such services as a database server, but it can also mean a server dedicated to providing other types of data, not just databases.