Bearing capacity of soils cannot be improved by A. Draining sub-soil water B. Ramming crushed stone in soil C. Driving sand piles D. Watering surface of soil

The correct answer is D. Watering surface of soil.

The bearing capacity of soil is the maximum load that a soil can support without failing. It is affected by a number of factors, including the type of soil, the moisture content of the soil, and the presence of any underlying layers.

Draining sub-soil water will reduce the moisture content of the soil, which will increase its bearing capacity. Ramming crushed stone in soil will create a more stable foundation, which will also increase the bearing capacity. Driving sand piles will create a more uniform surface, which will also increase the bearing capacity.

Watering the surface of soil will increase the moisture content of the soil, which will decrease its bearing capacity.

Therefore, the correct answer is D.