This movement is called convection. It can be found in liquids, gasses and rheids - solids that can also experience movement ( on a big time scale), such as the earth mantle. One of the types of convection is diffusion: net movement of gasses from higher to lower concentration areas.
A phalanx is a group of armed soldiers in ancient Greece arranged close together in rows.
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B? Human population are sometimes concentrated in areas that are lacking resources
Erosion can be controlled by building terraces. The correct option among all the options that are given in the question is the first option. The building of terraces prevents soil erosion by a good margin. It is mostly done in the hilly regions to stop erosion of soil by rain. I hope the answer helps you.
