To allow users to add new features without the ability to modify or delete existing ones, the feature service should have the "Create" and "Query" operations enabled. The "Create" operation permits users to add new features, while the "Query" operation allows them to view existing features. By not enabling the "Update" and "Delete" operations, users are restricted from making changes to or removing existing features. This configuration is ideal for workflows where data integrity is crucial, and only the addition of new data is permitted.​

Enabling "Update and sync" (Option A) would allow users to modify existing features and synchronize changes, which is not desired in this scenario. "Extract and create" (Option C) is not a standard combination of operations for controlling editing permissions in feature services.​

Reference Source: ArcGIS Server documentation on editor permissions for feature services