Which Field/Value pair will return only events found in the index named security?

The correct choice is associated with the specific syntax used in Splunk's Search Processing Language (SPL) to query indexed data. The SPL uses lowercase for certain keywords, specifically "index." This means that "index=Security" will not yield the desired results due to the capitalization of "Index." The correct syntax requires "index" to be in all lowercase, followed by an equal sign and the index name. Therefore, "index=Security" is the only option that correctly specifies the index named "security."

Additionally, the other options either have incorrect capitalization or use logical operators that do not fit the requirements. The "index!=Security" option suggests the exclusion of the index named "Security," which is not what is needed. The goal is to retrieve events from the specified index, not to exclude them.