Read the Following Scenario and Answer the Question Below

Read the following scenario and answer the question below.
The Intergovernmental Panel on Climate Change reported that physical, biological, and economic evidence exists confirming global climate change due to human-produced greenhouse gases. Although the United States emits most of Earth's carbon dioxide, its policies do not reflect concern over its environmental effects. The United States failed to ratify the Kyoto Protocol, an international agreement signed by other developed nations to reduce carbon dioxide emissions. Requested voluntary reductions of carbon dioxide emissions have not been effective in reducing greenhouse gases. Revisions to the 1970 Clean Air Act, called the "Clear Skies Initiative," were proposed to limit mercury, nitric oxides, and sulfur oxide emissions from power plants. Nicknamed by Robert F. Kennedy, Jr., as the "Clear Lies Initiative," this proposal did not specifically address emission of carbon dioxide, and its loopholes excluded older power plants from having to modernize, seemingly supporting pollutive industries with political influence. Environmentalists are arguing for immediate action, including stricter laws to limit power plant carbon dioxide emissions and subsidies for renewable energy. They favor "portfolio standards," requiring electric companies to provide clean energy alternatives to consumers and "green tags," "wind certificates," and "green pricing" to support the use of alternative fuels.
-Of the following greenhouse gases, which one has experienced the greatest percentage increase since 1750?

A) methane
B) ozone
C) water vapor
D) carbon dioxide
E) nitrous oxide