The percentage of space not occupied by solid matter in soil is called :
B. Porosity.
Explanation:
Porosity is represented as the percentage of void in the soil.In simple words, it is the number of pores present in a soil.The porosity of soil is a factor that determines the quality and suitability of the soil for agriculture.A more porous soil does not hold lot of water and nutrient while a less porous soil retains water and nutrient.Thus neither a extremely porous nor a less porous soil is suitable for agriculture.