Human activities are responsible for almost all of the increase in greenhouse gases in the atmosphere over the last 150 years. If we review the pie chart, we can determine the source greenhouse gas emissions by percentages. But ultimately, there is one huge cause of these emissions: it is involved with every piece of this pie chart. What is this human activity? A) the production of electricity B) the combustion of fossil fuels C) overpopulation in U. S. cities. D) the production of food for U. S. citizens