The answer is mean!
mean is the average of a group of numbers; therefore, it is the most efficient and accurate!
Hope this helps!! :)
The correct answer is a nutrient runoff.
Nutrient runoff is a major reason for eutrophication of surface waters, in which extra amount of nutrients, generally phosphorus or nitrogen, instigate growth of algae. Sources of nutrient pollution involve surface runoff from pastures and farm fields, emissions from combustion, and discharges from septic tanks.
I would say A since it is closest to the mouth of the volcano and says 20 cm