Landfills are waste disposal sites. They are often man made depressions in the ground covered with a lining designed to prevent any leakage of waste materials. However, landfills can leak through the base resulting in negative impacts on the surrounding environments. What negative impact to the environment is caused by the production of methane gas in landfills?

Select one:
a. air pollution
b. soil fertility
c. groundwater pollution
d. air pollution, groundwater pollution, soil fertility