Which animal passes a water current through its body for food?

Which type of cells are absent in sponges?

Assertion $(A):$ The body of sponges is supported by a skeleton.
Reason $(R):$ The skeleton of sponges is made up of spicules and spongin fibres.

Which phylum of animals,despite being multicellular in structure,does not exhibit division of labor?

The classification of $Porifera$ is based on $..........$.

The peculiarity of sponges is