Answer:
Agriculture allowed people to stay in one place, and increased food production caused the population density to expand far beyond levels that could be sustained by hunting and gathering alone. This growth in population density provided a critical mass of people to sustain and spread contagious infectious diseases.
Answer: B. It is useful for navigation.
Explanation:
The Mercator is a famous map projections that was created by Geradus Mercator who was a Flemish geographer in 1569.
The Mercator is used for nautical purposes and is regarded as the standard map projection due to the fact that the lines of true direction can be represented on it and hence useful for navigation.
Sand sheets and dunes cover approximately 25 percent of the Sahara's surface.
