Desertification affects a large number of people living in ______ countries.
Desertification affects a large number of people living in 168 countries, according to new research released by the UN Desertification Convention (UNCCD). "Desertification, land poverty and need is a matter of market failure. The lack of economic market valuation has led to land being supposed as a cheap resource." The causes of land degradation are wide-ranging, but are widely official to drought, climate change, demanding farming practices and poor water management.
Thus, the correct option is D.