The correct answer is: B. capillary water.
Capillary water is the water that is held in the soil by capillary action. This is the force that draws water up through the soil, against the force of gravity. Capillary water is the most important form of water for plants, as it is the water that they can absorb through their roots.
Gravity water is the water that is held in the soil by gravity. This is the water that is found in the pores of the soil, and it is the water that drains away from the soil when it rains. Gravity water is not available to plants, as it is too far below the surface of the soil for them to reach.
Hydroscopic water is the water that is held to the surface of soil particles by hydrogen bonds. This is the water that is found in the very smallest pores of the soil, and it is the water that is the most difficult for plants to absorb.
Chemical water is the water that is combined with minerals in the soil. This is the water that is not available to plants, as it is chemically bonded to the minerals.
In conclusion, the water utilizable by plants is available in soils mainly in the form of capillary water. This is the water that is held in the soil by capillary action, and it is the water that plants can absorb through their roots.