What does the repetition of concave and convex areas on the fa$$ade of Borromini's San Carlo alle Quattro Fontane do$?$

a$.)$

It makes the building feel more static and timeless.

b$.)$

It brings the building down to a more human scale.

c$.)$

It makes the building feel more monumental.

d$.)$

It creates a feeling of movement.