Answer: C. Measure the soil's volume and then the volume of water that the soil can absorb.
Soil porosity can be defined as the amount of pores or air spaces present inside the soil mass. These pores forms due to the movement of roots, earthworms and insects inside the soil. These pores helps in aeration of the soil and water retention. Both of these factors helps in the growth of the plants.
Porosity can be judged by the measuring the soil's volume and then the volume of water that the soil can absorb. The volume of water found in the soil will depend upon the amount of pores present in the soil hence, reflecting the porosity of the soil.