The cell cycle must be regulated in a multicellular organism in order to
a. maintain the proper cell number in tissues
b. activate cell division when repair of a tissue is needed
c. halt cell division when repair of a tissue is complete
d. prevent cancer
e. all of the above

The correct answer is E. all of the above

Explanation:

The cell cycle has several checkpoints that helps in the regulation of the cell cycle. Cell cycle regulation is important because if the cell cycle is not regulated then the cell will constantly divide which will be a waste of energy and an abnormal increase in the number of cells can do damage to the tissue. So regulation is important to maintain a proper cell number in the tissue.

Cell division helps in repairing the damaged tissue, therefore, cell division must be stopped after tissue is repaired and regulation is also important to prevent cancer because cell division stops when the mutation occurs in the cell's genetic material. Therefore the correct answer is E.

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.