A diagram in the course handout shows that a rotifer has a body cavity derived from blastocoel and not fully lined by mesoderm. Identify the related structure or process.

Rotifers are pseudocoelomate animals. Their pseudocoelom provides internal space and support but is not a true coelom completely lined by mesoderm. This MCQ belongs to the Rotifera topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.