a) 0.20
b) 0.25
c) 0.30
d) 0.35

Answer: d
Explanation: Consider a unit cube of soil having spherical particles of diameter d.
Volume of the solids V_s= (π/6)=0.5236
The total volume V=(1-cosα)*(√(1+2cosα))
Minimum void ratio is possible in densest state with α=60°
V=(1-cos60°)*(√(1+2cos60°))
V=0.7071
Volume of the voids V_v=V-V_s=0.7071-0.5236
V_v=0.1835
Voids ratio e= V_v/ V_s=0.1835/0.5236
e=0.35.