C. Permafrost
Permafrost is the layer beneath the "active layer". The active layer consists of soil that freezes and thaws every year. However, the requirement for permafrost is that it be frozen for two or more years consecutively. This is why permafrost exists in cold environments such as tundras.
<em>A<u> population </u>is a group of the same kind of living things in a ecosystem.</em>
<em>~I hope this helps! ;)</em>
Answer:
Human activities have a tremendous impact on the carbon cycle. Burning fossil fuels, changing land use, and using limestone to make concrete all transfer significant quantities of carbon into the atmosphere
<u><em>Answer: The Calvin cycle is a process that plants and algae use to turn carbon dioxide from the air.</em></u>
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<u><em>hope its helps you.</em></u>
<u><em> keep smiling be happy stay safe</em></u>
