Answer
correct answer is c) a natural phenomenon that has been enhanced by human activity
Work Step by Step
The greenhouse effect is a natural phenomenon in which a part of sun's energy is absorbed and reflected back through the surface of the earth certain cases called green house gases as we have discussed in the previous question Methane (CH4) , Carbon dioxide (CO2) , Ozone (O3) and nitrous oxide (NO2) allow the sunlight to shine in the surface and then ozone trap the heat that reflect back from the earth surface inside the atmosphere it is actually a phenomenon which is allowing life to occur on the planet but due to human activities the global warming is causing the earth's average temperature to rise every year because of increase of CO2 , O3 in the atmosphere it is also causing the climate change and which is harmful to the environment and people.
