_____ datasets can be added to a root dataset to narrow down the search.

The correct choice is child datasets because they are specifically designed to refine and narrow down the search results from a root dataset. In the context of Splunk, a root dataset serves as the overarching collection of data, and adding child datasets allows users to filter this data further based on more specific criteria or attributes.

Child datasets can represent more granular subsets of the data, such as specific fields, filtered results, or sample sets, which enhance the ability to perform targeted searches within the broader dataset. This hierarchical relationship enables users to maintain structure in their data organization and improve the efficiency of their searches.

For instance, if the root dataset contains all user activity logs, a child dataset might contain only those logs relating to a specific user or time frame. This focused approach helps in generating more relevant results and insights without needing to sift through the entire root dataset.

The other options do not accurately describe the datasets that can serve this purpose. Event datasets pertain to raw data points while extracted datasets relate to fields derived from events, and parent datasets would refer to the overall category being referenced, rather than a subset for filtering.