Answer:
Carbon
Step-by-step explanation:
Human activities are known to substantially alter the carbon cycle. New strategies applied to land-use systems, burning fossil fuels, and the use of limestone as building material are activities that emit high amounts of carbon into the atmosphere. It is well known that the excess of carbon as carbon dioxide (CO2) into the atmosphere warms the planet because this gas is an important heat-trapping (greenhouse) gas. Moreover, it is also important to note that deforestation also affects the carbon cycle since plants use CO2 during photosynthesis.