The type of sanitary landfill that should be developed on essentially flat land sited in dry areas is:

The correct choice is area landfills. Area landfills are designed to be constructed in flat terrains, which allows for efficient waste disposal and management. These landfills work well in dry areas because the lack of excessive moisture can reduce leachate generation, thus minimizing the potential for groundwater contamination. Additionally, the flat land makes it easier to manage the waste placement, cover, and compaction, increasing the overall efficiency of the landfill operation.

In contrast, depression landfills typically utilize natural depressions to contain waste, which may not be ideal for flat land. Progressive excavation landfills often involve active excavation processes, which are not as effective in flat, dry areas. Cut and cover landfills involve burying waste beneath the surface, typically in urban areas where land use is at a premium. This technique is not suited for flat, dry regions where an area landfill could be implemented more effectively.