In 2015 the New York City Mayor's office reported that the city had recently accomplished the following:
.
.
.
Reduced carbon emissions by one-fifth and achieved the
city's cleanest air in 50 years
Upgraded building codes to prepare for extreme weather
like flooding and high winds
Added nearly one million trees and six million square feet
of reflective rooftop to the city landscape
D) 25.
Which challenges prompted New York City to take these actions?