The Sorter transformation can be configured with the 'Distinct' output option to treat output rows as distinct, removing duplicates during the sort operation. When enabled, the Sorter uses the sort key columns to identify and eliminate duplicate rows, passing only unique rows to downstream transformations. This is more efficient than using an Aggregator or Expression transformation after sorting to remove duplicates. The other options are incorrect: duplicates are not rejected, they can be eliminated; there's no case-based duplicate sorting behavior.