The correct answer is option 'B': Capillary water.

Explanation:
In soil, the water available for root absorption is capillary water. Capillary water refers to the water that is held in the soil pores against the force of gravity and is accessible to plant roots. It is the water that plants can readily absorb and use for their growth and development.

Here is a detailed explanation of the different types of water present in soil:

1. Gravitational water: When it rains or when soil is irrigated, some water percolates deeper into the soil due to the force of gravity. This water moves downwards through the soil profile and is not accessible to plant roots. It drains away through the soil layers and eventually reaches the groundwater table.

2. Capillary water: Capillary water is the water that is held in the soil pores against the force of gravity. It is retained in the soil due to capillary forces, which are the result of the attraction between water molecules and soil particles. Capillary water fills the small spaces between soil particles and is readily available for plant roots to absorb. The capillary forces allow the water to move upward against gravity, providing a continuous water supply to the roots.

3. Hygroscopic water: Hygroscopic water is the water that is held tightly by the soil particles and is not available for plant roots. It is essentially bound to the soil particles and cannot be absorbed by plants. This water is held at extremely high tensions and is not accessible to plants even under normal soil moisture conditions.

4. Combined water: Combined water refers to the water that is chemically combined with the soil minerals. It is not available for plant uptake as it is tightly held and cannot be easily released.

In summary, capillary water is the water that is readily available for plant roots to absorb in soil. It is held in the soil pores against the force of gravity and provides plants with the necessary moisture for their growth and development.