What component directly retrieves data when a user selects a country?

The component that directly retrieves data when a user selects a country is the "GetCountries Aggregate." This is because aggregates in OutSystems are used to fetch data from the database and return it to the application. When a user selects a country, the application needs to retrieve related data, such as cities or other information linked to that specific country.

In this context, the GetCountries Aggregate is responsible for querying the database and returning a list of countries or related entities that can be filtered based on the user's selection. This is a crucial part of the data retrieval process, ensuring that the user sees relevant information instantly.

The On Fetch event typically refers to an event triggered during the data retrieval process but does not directly retrieve data itself. GetCities Aggregate would be focused on fetching cities, potentially based on the selected country, but it does not serve the direct purpose of retrieving country information. An Input Parameter is a way to pass data into a server action or function but does not retrieve data on its own. Therefore, the GetCountries Aggregate is the correct component designed specifically to handle the retrieval of country data in response to a user selection.