Answer:
Temperatures across 98 percent of Earth's surface were hotter at the end of the 20th century than at any time in the previous 2,000 years. Such nearly universal warming, occurring in lockstep across the planet, is unique to this current era, scientists say
Explanation:
I think B but I might be ! wrong !
You cant settle in deserts due to lack of water and scarcity of food, which led to the Saharan regions being less populated. Hope this helps.