Answer:
The correct answer is the third statement, that is, when the heated substance gets near to the surface, it starts to cool.
Step-by-step explanation:
A current that arises within a fluid due to convection is termed as the convection current. In comparison to the surface, the core is extremely hot, thus, both core and the surface exhibit very distinct temperatures. The mantle rises towards the surface when it gets heated as it moves close to the core. However, when it moves towards the surface, the mantle starts to turn cool and denser.
Afterward, the magma, which is cool, again then begins to move close to the core, and gets heated and rises again, this phenomenon results in the emergence of convection currents.