The b horizon is

a. rockier than the c horizon
c. less nutrient rich than the a horizon
b. richer in humus than the a horizon
d. thicker than the c horizon

less nutrient rich than the A horizon

Explanation:

B horizon is the layer of the soil present below the uppermost horizon (the A horizon). B horizon is characterized by the presence of lesser amount of humus as compared to the humus present in A horizon. The lesser humus content in B horizon makes it less nutrient-rich compared to the A horizon. B horizon is a hard and compact soil layer.

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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."