A flat slab is supported A. On beams B. On columns C. On beams and columns D. On columns monolithically built with slab

The correct answer is: D. On columns monolithically built with slab

A flat slab is a type of concrete slab that is supported directly by columns. The slab and columns are poured together as a single unit, which creates a monolithic structure. This type of construction is often used in commercial and industrial buildings, as it can provide a large, open floor plan with minimal columns.

The other options are incorrect because:

• A flat slab is not supported on beams.
• A flat slab is not supported on columns only.
• A flat slab is not supported on columns that are not monolithically built with the slab.