Which of the following is considered the simplest animal?

sponge
cnidarian
arthropod
roundworm

Sponge

Explanation:

As the sponge is included in phylum Porifera they are the simplest animal. They contain holes in their body and marine animal. Water passes through these pores and nutrients absorbed from the water. So, in the above option sponge is the simplest animal.

rocks and weathering-matching

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