Correct Answer - Option 3 : 1

__Concept:__

Void ratio (e):

Void ratio is usually defined as the ratio of the volume of voids to the total volume of soil solid.

Porosity (n):

Porosity is defined as the ratio of the volume of voids to the total volume of the soil.

The relationship between void ratio and porosity are as follows:

\(\rm{e=\frac{n}{1-n}\; and\; n=\frac{e}{1+e}}\)

__Calculation:__

η = Porosity = 0.5

From the above equation;

\(e = \frac{n}{{1 - n}}\)

\(e = \frac{0.5}{{1 - 0.5}}\)

**e = 1**