Which statement best describes the hydrosphere? A it includes only the water on the Earth's surface
B It includes only freshwater on the Earth's surface
C It includes water on the Earth's surface, underground, and in the atmosphere
D It includes fresh and salt water on the Earth's surface and underground

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.

a

explanation: