The convection currents are formed due to heating of molecules.
When the liquid molecules are heated, the liquid becomes larger in size and lighter in weight. The heated molecules take up more space and rise to the top, while the cooler molecules comes to the bottom and takes the place. This cycle is known as the convection current.
Convection currents are the result of differential heating. Lighter which is less dense and warm material goes upward while on the other hand, heavier which is more dense and cool material sinks. This movement creates circulation patterns known as convection currents in the atmosphere.
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Fold mountains occur on Collison zone plate boundaries, where two continental plates collide with each other, causing them to rise up
Productive Resources are resources used to make goods and services.
Therefore the best possible option is the last one - Factors that are used to make goods and services.
The perennial system is less dependent on the Nile flood and allows the planting of multiple crops. (source: another brainly question)
