Today, the annual rate of tectonic plates movement is observed and measured by satellites.
So, the answer is option A. Satellites.
~Hope this helps!
The correct answer is - B) convection currents in the mantle.
There's multiple tectonic plates on the surface on the planet, around 17 from what is known so far, but as the scientific methods are developing there might be few more discovered in the years to come.
These plates are all moving, only few cm per year, but on the long term it influences and changes everything on the surface on the Earth.
The movement of the plates is the result of the convection currents in the mantle layer beneath. These convection currents are essentially the combination of the high temperatures, high pressures, and viscous metals, and they managed to break up the crust on the surface, and with its push force, they are slowly moving the plates.
With the movement of the plates and their collisions and moving away, lots of earthquakes and volcanoes are appearing all over the plate boundaries.
I think it is the first one
