The correct option is A A- r, B- p, C- q
A flame cell is a specialized excretory cell found in the simplest freshwater invertebrates including flatworms. So, it is present in Planaria.
Collar cells are cells that line the interior of asconoid, synconoid and leuconoid body type sponges.
Along with jellyfish, sea anemones and corals, hydra is a part of animal phyla Cnidaria, who use stinging cells to catch prey.
So, the correct answer is option A.