Some "cleaner fish" consume parasites and mucus from the skin of larger fish. What would be a reasonable argument for why this could be a mutualism rather than a commensal relationship? (3 points)

The cleaner fish prefer to consume mucus from the larger fish rather than parasites.
The cleaner fish reduce the number of parasites on the larger fish.
The larger fish are healthier when the cleaner fish are not present.
The larger fish have no difference in parasite load when the cleaner fish are present.