? refers to the complex designs, such as ovoids and split Us, that are the underlying components of Northwest Coast art. O a. Petroglyph
O b. Formline
O c. Graphics
O d. Ravenstail

the correct answer for this question is:

it is system invented in 1872 that produced the first illusion of movement. basically it was a disk with a series of drawings around the edge, showing the same object in slightly different poses. when it was spun, it created the illusion of movement.

found this online : )