What structure does phylum Cnidaria have that no other phylum does?

Explanation:

Cnidarians are radially symmetrical (i.e., similar parts are arranged symmetrically around a central axis). They lack cephalization (concentration of sensory organs in a head), their bodies have two cell layers rather than the three of so-called higher animals, and the saclike coelenteron has one opening (the mouth).

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

yes!

explanation:

because it has a type of fat that can make you extremely sick