Both indices quantify the state of cohesive soil based on its natural water content.

When $w_n = w_L$, $I_L = 1$ and $I_C = 0$.

When $w_n = w_p$, $I_L = 0$ and $I_C = 1$.

These indices are only applicable to fine-grained (cohesive) soils.

Provides immediate insight into the physical state of soil relative to its limits.

Standardized index system used globally for geotechnical site characterization.

Does not account for non-cohesive or granular soils where plasticity is absent.

Highly dependent on the accuracy of liquid and plastic limit laboratory testing.

Predicting soil strength, compressibility, and sensitivity.

Used in highway and foundation engineering for classifying clays.

The indices reflect the range of consistency from liquid state ($I_L > 1$) to solid state ($I_C > 1$).

Option B is correct because the algebraic sum of the numerators ($w_n - w_p + w_L - w_n$) exactly equals the denominator ($w_L - w_p$).