The correct option is A Turbellarians
The Turbellaria are one of the traditional subdivisions of the phylum Platyhelminthes and include all the sub-groups that are exclusively not parasitic. The name 'Turbellaria' refers to the 'whirlpools, of the microscopic particles created close to the skins of the aquatic species by the movement of their cilia.
So, the correct answer is option A.