EVERYDAY SCIENCE

Detailed explanation-1: -So, the correct option is ‘Sponges’.

Detailed explanation-2: -Cnidarians are the most primitive “true” multicellular animals (Subkingdom Eumetazoa). They are radially symmetric, and can be either sessile or motile, and sometimes both (at different stages in their life cycles).

Detailed explanation-3: -Phylum Porifera is a group of simple animals that includes the sponges. Porifera have no internal organs, nervous tissue, circulatory system, or digestive systems, making them the most primitive of the multi-cellular animals.

Detailed explanation-4: -Sponges belong to the phylum Porifera. Sponges are primitive multicellular animals and have a cellular level of organization.

Detailed explanation-5: -Sponges are considered to be one of the simplest animals, primarily because their bodies are not organized in organ systems or even tissues. Rather, sponges are made up of a grouping of cells that work together to contribute to meeting the daily needs of the sponge.