Concept:Flame cells are specialised excretory structures found in flatworms, which include flukes.Explanation:Flame cells beat like tiny flames to move waste fluids out of the body.They remove excess water and nitrogenous waste.Flukes are flatworms (Platyhelminthes), so they possess flame cells.Nematodes do not have true flame cells.Bacteria and Volvox lack such specialised excretory organs.Answer:A. Fluke