How do landfills contribute to global warming? a. they keep people from recycling. b. animals become dependent on landfills for resources. c. they take up valuable space. d. they produce methane, a greenhouse gas.

The correct answer would be option D.

Landfills contribute to global warming by producing greenhouse gases such as methane and carbon dioxide.

Landfills are the places where waste materials are stored and degraded.  

The waste materials contain a high amount of organic matter decomposition of which results in the production of gases such as methane and carbon dioxide.

These gases get accumulated in the atmosphere and contribute to global warming.