Final answer:
The movement of tectonic plates is primarily driven by C) convection currents in the asthenosphere, related to the transfer of heat from the Earth's interior.
Step-by-step explanation:
The movement of tectonic plates is most commonly believed by scientists to be driven by C) convection currents in the asthenosphere. This is a region of the Earth's mantle where temperatures and pressures allow for the rock to flow slowly over time. These convection currents are caused by the heat escaping from the interior of the Earth, creating an upward flow of warmer material and the downward sinking of cooler material.
Alternative mechanisms mentioned in the question, such as tidal motions in the hydrosphere or density differences in the troposphere, are not considered primary drivers of tectonic plate movement. The solidification in the lithosphere, while it contributes to the structure of tectonic plates, is not a driving force for their movement either.