Final answer:
Our current knowledge of plate movement is known to be approximately 5 cm per year.
Step-by-step explanation:
Geoscientists have measured plate movements with various techniques such as global positioning satellites (GPS) and very-long baseline interferometry (VLBI). These measurements provide data on the rates of motion between tectonic plates. Based on these measurements, we know that the average rate of plate movement is about 5 cm per year. Therefore, the correct answer is c) 5 cm per year.