Correct Answer - Option 1 : increases with an increase in the liquid limit.

__Explanation:__

For undisturbed low to medium sensitivity soils, the coefficient of compression or compression index (Terzaghi and Peck empirical index)

Cc = 0.009(LL - 10)

For disturbed low to medium sensitive soil (Skempton's empirical index)

Cc = 0.007(LL - 10)

So, If the liquid limit is increased then, the compression index of soil will increase.

Compression Index:

- The compression index (Cc) is the slope of the linear portion of the pressure–void ratio curve on a semi-log plot, with pressure on the log scale (IS: 8009 – Part 1, 1976).
- This is a dimensionless parameter.
- For any two points on the linear portion of the plot-

\({C_c} = \frac{{{e_o} - {e_1}}}{{\log \left( {\frac{{{p_1}}}{{{p_o}}}} \right)}}\)

Where

po and p1 are pressures corresponding to e0 and e1 respectively