What is a source that can be used to create a composite locator?

A composite locator is a type of locator in ArcGIS Pro that combines multiple address locators, allowing for more comprehensive geocoding by leveraging the strengths of each underlying locator. Specifically, using other locators as a source is ideal because it enables the composite locator to reference various address formats, geographic areas, or datasets, thereby improving the accuracy and coverage of geocoding results.

When creating a composite locator, you typically aggregate multiple locators that may specialize in different geographical regions or formats of address data. For instance, one locator might focus on urban areas, while another covers rural regions. This versatility is crucial in applications where users may deal with a wide range of address formats or geographical contexts.

As for the other choices, they have varying degrees of relevance but do not serve the primary function needed for creating a composite locator. Input data with addresses can be useful for geocoding but does not constitute a locator itself. Reference data with addresses could provide additional context or validation for geocoding results but is not directly used to create locators. Online locator services are external resources but would not be combined directly into a composite locator within ArcGIS Pro.