Concept:On a topographical map, colours are used to represent different natural and human features.Explanation:Blue is conventionally used to show water-related features such as rivers, lakes, streams, and other bodies of water.Buildings and construction are usually shown in black or red, mountains and hills are shown by contour lines or brown shading, and rocks and stones are often shown in grey or black.Therefore, the feature indicated by blue is water.Answer:B. rivers and lakes