1. How does the thaumatrope allow images to merge? A. by twirling

B. with 3D vision

C. by flipping back and forth between images

D. it uses a rotating trick

(A) By twirling

More information:-

The thaumatrope is the most basic of motion toys. It consists of a disc that is attached to two pieces of string. When twirled, the images on the sides of the disc are perceived together as a single image. Like all animation devices, the thaumatrope works on the principle of persistence of vision.