The correct answer is C. sheep foot roller.
A sheep foot roller is a type of roller that has a series of large, flat plates or feet that are attached to the drum. These feet press into the soil and compact it. Sheep foot rollers are ideal for compacting clayey soils because they can penetrate the soil deeply and provide uniform compaction.
A smooth wheeled roller is a type of roller that has a smooth, cylindrical drum. This type of roller is not as effective for compacting clayey soils as a sheep foot roller because it does not penetrate the soil as deeply.
A pneumatic tyred roller is a type of roller that has large, pneumatic tires. These tires provide a cushioning effect that helps to prevent the soil from being compacted too much. Pneumatic tyred rollers are not as effective for compacting clayey soils as a sheep foot roller because they do not provide as much penetration.
A vibrator is a type of equipment that uses vibration to compact soil. Vibrators are not as effective for compacting clayey soils as a sheep foot roller because they do not provide as much penetration.
In conclusion, the most suitable equipment for compacting clayey soils is a sheep foot roller.