Which characteristic is shared by both cnidarians and flatworms?

a) dorsoventrally flattened bodies
b) flame cells
c) radial symmetry
d) a digestive system with a single opening
e) both a and d

The answer is D: a digestive system with a single opening.

Cnidarians and flatworms have a digestive system with a single opening.

Explanation: Cnidarians are species of aquatic animals. They are mostly marine organisms that live in both marine and freshwater where they get food. Their respiration and digestion takes place through one orifice and a body cavity.

Flatworms are simple soft-bodied invertebrate animals. Their bodies are not divided into segments.  Flatworms depend on a large surface in order to allow oxygen and nutrition to diffuse into their bodies. They have a digestive system with a single opening. Their habitation are  in marine, freshwater, and damp terrestrial environments.

4.) metal

"-the movement of carbon from the nonliving environment into living things and back to the environment

-carbon is the essential component of proteins, fats, and carbohydrates (which make up all organisms)

-carbon exists in air, water, and living organisms

-producers convert carbon dioxide in the atmosphere into carbohydrates during photosynthesis

-bacteria in the atmosphere cycles through the system in filtration units

-in cellular respiration, carbon is released back into the atmosphere as carbon dioxide

-some carbon is stored in limestone (forming one of the largest "carbon sinks" on earth)

-largest carbon reservoir on earth= limestone

-carbon stored in the bodies of organisms as fat, oils, or other molecules may be released into the soil or air when the organism dies

-this may form deposits of coal, oil, or natural gas (fossil fuels, which increased the atmospheric carbon dioxide)

-fossil fuels store carbon left over from bodies of organisms that died millions of years ago

-they are located in the surface of earth, deep within the earth and beneath the ocean floor."