How does the Include method work in the RelatedData API?

The Include method in the RelatedData API is designed to efficiently load related items that are linked through navigation properties within the data structure. The key feature of this method is its reliance on established navigation properties to fetch the associated entities without the need for additional queries.

When considering the other choices, the first option suggests that it retrieves all related items, which is misleading because the Include method specifically targets the related items defined by the navigation properties, rather than indiscriminately loading every related entity. The third choice states that it only works with predefined relations, which is partially true, but it does not specify the significance of navigation properties that must exist for the Include method to function correctly. Lastly, the idea that the Include method needs an additional query is not accurate; it operates by enhancing a single query to include necessary related data, rather than requiring separate calls.

Thus, the correct understanding is that the Include method is contingent on available navigation properties to successfully load related data, highlighting its effective design within the API for optimized data handling.