Describe how scientists can directly measure the movement of tectonic plates

The Earth's lithosphere is differentiated into small fragments of plates that float on and travel autonomously over the mantle, and the majority of the seismic activity of the Earth takes place at the boundaries of these plates. These plates are known as tectonic plates. In order to determine the movement of plates, scientists can use a combination of satellites and lasers. By focusing lasers on the ground with the help of satellites, the scientists can find the Earth's plates movements, which are as small as a single centimeter per annum.

correct answer is a. and d.

i think its y= -4x-14