Cnidarians and Ctenophores are alike in the following way: a) they are scavengers and parasites. b) they are both diploblastic. c) both groups move with simple contractions of the bell. d) some members of both groups secrete supportive exoskeletons. e) they both alternate between bilateral and radial forms.

Options B.

They are both diploblastic.

Explanation:

Cnidarians are group of aquatic animals that live both in fresh water and Marine water. They are distinguished by the possession of specialized cells called cnidocytes for capturing prey. They are radially symmetrical and have two body layers ectoderm and endoderm separated by jelly layer called mesoglea.

Examples are Hydra, corals, sea anemone and jelly fish.

Ctenophores are phylum of Marine animals that are found in every where. They are characterized by vast of cilia which is use for swimming. They are bilaterally symmetrical , they have mouth and don't have anus. They don't have respiratory, excretory and circulatory system. They are diploblastic i.e they have two body layers but some are triploblastic.

They have nemacyctes for capturing prey.

Examples are nuda, tentaculata e.t.c.

they deliver oxygen to the blood

the rocks are classified by the geological process they are formed by. the three main groups of rocks are igneous, metamorphic, and sedimentary. minerals are not they are classified under the chemical classes they are in. these groups include silicates, sulfates and carbonates.