This about sponges is true

The correct option is "innumerable mouths, one exit".

To understand why this statement is true for sponges (phylum Porifera), we can look at their unique anatomical structure and how they filter water to survive:

1. Innumerable Mouths (Ostia): Sponges have bodies filled with many tiny pores called ostia. These pores act as countless tiny "mouths" through which water containing food particles and oxygen is drawn into the sponge's body.
2. One Exit (Osculum): After water enters through the ostia and passes through the internal canals where nutrients are absorbed, it is directed into a central cavity called the spongocoel. From there, the water is expelled out of the sponge's body through a single, larger opening at the top called the osculum, which acts as the single "exit".

Let's briefly look at why the other options are incorrect:
- "One mouth, innumerable exits" is the exact opposite of how a sponge's water vascular system operates.
- "Spicules are composed of chitin" is incorrect because sponge spicules are typically made of silica (glass) or calcium carbonate, not chitin (which is found in fungi and arthropod exoskeletons).
- "Large spacious stomach" is incorrect because sponges do not have true tissues, organs, or a digestive tract (stomach); instead, digestion occurs at the cellular level (intracellular digestion).