The correct answer is (a) Low lying areas
To explain: Low lying areas are usually used to dispose the urban waste which is present near the sea level whereas, any type of waste cannot be disposed of in residential areas of towns and cities or industrial areas which generate a lot of waste like glass, domestic waste, food waste, metals, tin, leaves etc. are referred to as urban waste or in rural areas, as it may pose a threat to the humans and organism living in those areas.