Strategies being used to reduce pollution in Sub-Saharan Africa include
cleaner-burning fuels
increased air travel
more efficient cars
increased development
UNFCCC

The answer i think is d

The us is first  the  u.s. economy  remains the  largest in the world  in terms of nominal  gdp. however, the  u.s. economy  loses its spot as the number one  economy  to china when  measured  in terms of  gdp  based on ppp. in these terms, china's  gdp  is $23.19 trillion exceeds the  u.s. gdp  of $19.42 trillion