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What is the importance of using Hazard Maps to people and volcanologists?

Hazard maps are important to people so they can be aware of dangerous conditions in the areas where they live or are planning to visit. They should stay out of dangerous areas unless they have the training and equipment that they require if it is necessary for their job-- such as firefighters or research scientists.

Volcanologists can use maps to see how conditions have changed over the years. A map from 20, 50 or 100 years ago will show the hazards that existed when the map was made. The volcanologist can compare it with more maps and current conditions. The volcanologist might use the hazard map to deliberately choose a place to go to gather data relating to a hazard for study.  

i don't understand. explain it clearly

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2