Answer: A They have increased the population of green house gases.
Step-by-step explanation:
The human population has exerted a negative impact over the atmosphere in last 200 years by conducting activities like burning of fossil fuels, deforestation which have contributed to increase in abundance of greenhouse gases. The greenhouse gases like carbon dioxide, carbon monoxide, methane are capable of traping the heat energy from sunlight. As a result of this the temperture of the atmosphere has raised globally. With the increase in the population worldwide the demand for fossil fuel as a source of energy has increased. Therefore, the level of greenhouse gas has also increased since past 200 years.