Correct option is (b) 47.64%
To explain I would say: Consider a unit cube of soil having spherical particles of diameter d.
Volume of each spherical particle = (π/6)d^3
Total volume of container = 1*1*1=1
No. of solids in the container = (1/d)*(1/d)*(1/d)=(1/d^3)
Volume of the solids Vs = (π/6)*d^3*(1/d^3)=(π/6)
Volume of the voids Vv = 1-(π/6)
Voids ratio e = (1-(π/6))/(π/6)
Porosity n = e/(1+e) = 0.9099/(+0.9099) = 0.4764
In percentage, n = 47.64%.