Answer:
The correct answer would be B) the flow of water through the body of a sponge.
Sponges are multi-cellular organisms which are devoid of organ systems like digestive system, nervous system, circulatory system et cetera.
They have a unique feeding system in which they keep constant water flow through their bodies. They obtain food and oxygen and remove waste through this water movement.
The movement of water throughout the sponge is unidirectional in nature. It enters the sponge body through ostia and exit from the osculum.
As the water is pumped out, the cells present in the walls filter out the food present in the water.
