The correct answer is: B. Franki pile.
A Franki pile is a type of deep foundation that is constructed by driving a steel tube into the ground and then filling it with concrete under pressure. The concrete is compacted by compressed air, which is forced into the tube through a series of holes in the bottom. This process ensures that the concrete is dense and well-compacted, which provides a strong foundation for buildings and other structures.
Simplex piles are driven into the ground by a hammer, and the concrete is poured into the hole after the pile is in place. Pressure piles are driven into the ground by a hydraulic ram, and the concrete is poured into the hole before the pile is driven. Vibro piles are driven into the ground by a vibrator, and the concrete is poured into the hole after the pile is driven.
In conclusion, the compaction of concrete in the drilled pile hole is done by compressed air in the case of a Franki pile.