WORLD CIVILIZATION

“The Creation of a mosaic was a complicated procedure that called for careful timing and teamwork.Walls were painted with a resin before being covered with the first of 3 layers of plaster. A sketch of the art was then made on the plaster to serve as a guide for the various artisans. The outermost layer of the plaster, in which the pieces, or tessarae, of the mosiac were spread on only enough area to for a day’s work. Some of the tessarae-small, carefully cut fragments{small pieces} of colored glass, marble, and semiprecious stones-were pressed into the wet plaster so that they stuck out at a slight angle, so that they would reflect light and shimmer."Refer to the excerpt. Which sentence of this passage best states the main idea?