13. Scientists compared fossil remains of a species that lived 5,000 years ago with members of the same species living today. Scientists concluded that this species had changed very little
over the entire time period. Which statement best accounts for this lack of change?
A. The environment changed significantly and those offspring without favorable
characteristics died.
B. The environment changed significantly, but the species had no natural enemies for a
long period of time.
C. The environment did not change significantly and those offspring expressing new
characteristics survived their natural enemies.
D. The environment did not change significantly and those offspring expressing new
characteristics did not survive.

it enhances antibody production by t cells of the adaptive immune system.

hope i'm right

explanation:

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."    

the correct answer is 2 and 4