Acarbon atom has 6 electrons however, its valency is 4. this is because the carbon atom a. donates its 2 electrons to another atom b. shares its 2 electrons and bonds with another atom c. has 4 electrons in its first shell and 2 in the second shell d. has only 2 electrons in its first shell and 4 in the second shell

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.