Final answer:
The United Nations designates 50 countries in the bottom ranks of the low-income category as Least Developed Countries (LDCs).
Step-by-step explanation:
The United Nations designates 50 countries in the bottom ranks of the low-income category as Least Developed Countries (LDCs). LDCs are countries that have lower standards of living compared to more developed countries. They typically have lower per capita GDP and are characterized by poverty and the lack of modern industry.