b. perspective
The Renaissance technique Raphael used in School of Athens is called perspective. It is a technique that includes an architectural perspective with a vanishing point set in the middle of the whole painting. In the specific case, the vanishing point is where the central figures of Plato and Aristotle are standing. The painting, which is an affresco, is located in Italy, inside of the Vatican Museum, and it was painted between 1509-1511.