Raft foundation are generally preferred to when the area required for individual footing, is more than A. 25% to total area B. 30% of total area C. 40% to total area D. 50% of total area

The correct answer is: D. 50% of total area.

A raft foundation is a type of foundation that spreads the load of a structure over a large area. This is done by creating a concrete slab that is supported by footings or piers. Raft foundations are typically used in areas with poor soil conditions, such as areas with high water tables or expansive soils.

Raft foundations are generally preferred to when the area required for individual footings is more than 50% of the total area of the structure. This is because raft foundations are more efficient in terms of material usage and construction costs.

Option A: 25% of total area is not a large enough area to justify the use of a raft foundation.

Option B: 30% of total area is still not a large enough

Option C: 40% of total area is getting closer to the threshold where a raft foundation might be justified, but it is still not a definitive answer.

Option D: 50% of total area is