(a) Study Fig. 6.1 (Insert), which shows information about threats to the natural environment in the Caspian Sea. [Figure 6.1 (Insert) is a map showing the Caspian Sea and its surrounding areas. It indicates major urban areas (e.g., Atyrau, Bautino), major rivers flowing into the sea (e.g., Volga, Ural), oil and gas fields, and areas of pollution. A key specifies various sources of pollution.] (b) Study Figs. 6.2, 6.3 and 6.4 (Insert), which are photographs of economic activities which increase greenhouse gases in the atmosphere. [Figure 6.2 (Insert) is a photograph of a power station, likely coal-fired, with smoke stacks emitting plumes. Figure 6.3 (Insert) is a photograph showing grazing cattle in a field. Figure 6.4 (Insert) is a photograph of an area undergoing deforestation or showing logged trees.]