A geographer who studies how volcanic eruptions are shaping the Earth most often uses which of the six essential elements of geography?

physical systems

Explanation: The physical systems are one of the six essential elements of geography. These systems are the ones that are natural, and they shape the physical appearance of Earth because of its geological process. Part of these physical systems are the volcanoes with their eruptions. The Volcanoes are one of the major factors that influence the shaping of the Earth's surface, as they manage to propel enormous amounts of material from them, with the magma/lava being the one that usually covers the surface and creates new land forms. The volcanoes themselves create new forms, be it island chains or continental arcs.

there are no mutiple choices here

part a. there were 250 teenagers surveyed (100% of tenagers = 250)therefore 1 % = 250/100 = 2.5 76% = 1% x 76 = 2.5 x 76 = 190 teenagers of the 250 surveyed liked burgerspart b: jane surveyed 25% (which is equal to 50 teenagers, i.e. a quarter of the teenagers surveyed is 50) to get 100% we simply get 4 quarters, i.e. multiply 50 by 4 = 200 teenagers were surveyed by jane. part c: it is impossible to give an example where a percentage is greater than 100%, since, by definition , percentage means "per 100".