Correct Answer  Option 3 : C
Explanation:
Void ratio:
 It is the ratio of the volume of voids and the volume of solids in the soil.

\(e = \;\frac{{{V_v}}}{{{V_s}}}\), e > 0, but there is no upper limit for void ratio.
Porosity:
 It the ratio of the volume of voids and total volume of soil.
 \(n = \;\frac{{{V_v}}}{{{V_{}}}}\)
When, the volume of solids (V_{s}) = Volume of voids (V_{v})
Void ratio (e) = 1, By putting the V_{s} = V_{v} in the above formula
And we know, Porosity
\(n = \;\frac{e}{{1 + e}}\) = \(n = \;\frac{1}{{1 + 1}}\) = 0.5 OR 50 %