The most serious environmental damage that may result from our use of fossil fuels is

Of the many environmental and public health risks associated with burning fossil fuels, the most serious in terms of its universal and potentially irreversible consequences is global warming. In 2014, approximately 78 percent of US global warming emissions were energy-related emissions of carbon dioxide.

Explanation:

plato users:

d.  

there was a variety of food available on island x, but there were only large seeds and nuts on island y.