What types of pollution in the great lakes has human activity caused? check all that apply. a) industrial waste b) soil erosion c) sewage disposal d) runoff e) air pollution

20 points “the creation of a mosaic was a complicated procedure that called for careful timing and teamwork. . walls were painted with resin or tar before being covered with the first of three layers of plaster. . a sketch of the projected work was then made on the plaster to serve as a guide for the various artisans. the outermost layer of plaster, in which the pieces, or tesserae, of the mosaic would be set, was spread on only enough area to contain a day’s work. some of the tesserae—small, carefully cut fragments of colored glass, marble, and semiprecious stones—were pressed into the wet plaster so that they projected at a slight angle. the stones thereby better reflected light and imbued the finished mosaic with a shimmering life of its own.” —empires besieged: time frame a.d. 200–600 how many layers of materials were under the tiles? a. two- c. four- b. three- d. five