Which statement correctly explains what happens when two plates carrying oceanic crust meet at a trench. The plates crash head-on and both plates move downward returning to the mantle.

the plate that is less dense climbs above the other plate and forms new crust.

the plate that is more dense dives under the other plate and returns to the mantle.

The plates crash head-on and the collision squeezes the crust into mighty mountain ranges.

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.

occluded front i think