Correct answer is 4. Under 2.5 people per sq. mi. (VERY low density)
Explanation:
Option four is the correct because areas such as Sahara have a low density and are not populated. The conditions of living are not allowing people in these type of areas to create some larger permanent settlements. The similar case is for example in Australia where 3/4 is covered with desert, which is practically uninhabited. Or we can also created a parallel with Greenland which also has a low density due to climate factor.
