Which is an important issue the united states faces in the twenty-first century? a. terrorism b. global warming c. globalization d. all of the above

D all of the above
although Global Warming will take millions of years to affect the globe permanently and globalization is also not a problem because all 7+ billion people in the world could fit in the US city of Los Angeles. 

James wattrichard arkwright eli whitney thomas edisonnicolaus otto

The central idea is that the hiv/aids epidemic is serious.