Answer:
The correct answer is a) Density and temperature.
Step-by-step explanation:
The earth has a mantle between the nucleus and the crust that is divided into the inner mantle that is solid and elastic, and the outer mantle that is fluid and viscous.
In the mantle of the earth, the asthenosphere is identified, it is located below the lithosphere, which is characterized by its solid region and when influenced by high temperature, it becomes a moldable element, also by being closer to the surface of the earth's temperature can be 300 to 500 degrees Celsius.
Therefore, the density and temperature characteristics are the main cause of convection currents in the asthenosphere. Convection currents are distinguished by heat transfers from one site to another through moving fluids.
The convection currents in the asthenosphere are significant because through them, the movements of technical plates that have the function of the formation of mountains and the new life through the changes produced by the convection currents are produced.
I hope this information can help you.