Conductivity (specific conductance) is related to measured resistance and the geometric cell constant by the relation κ = (cell constant)/resistance, because conductivity equals conductance multiplied by the cell constant, and conductance is the reciprocal of resistance. Here the cell constant is 1.29 cm^-1 and the resistance is 100 ohm. Substituting, κ = 1.29/100 = 0.0129 S cm^-1. The cell constant accounts for the fixed distance between electrodes divided by their cross-sectional area, converting a raw conductance into an intrinsic property of the solution. Option 0.129 S cm^-1 results from dropping a factor of ten in the resistance. Option 0.00129 S cm^-1 divides by an extra factor of ten. Option 1.29 S cm^-1 ignores the resistance entirely. This is the standard NCERT conductometric calculation used to standardise cells with KCl. Working through the logic step by step, rather than memorising the result, makes it clear why resistance measurement governs the behaviour seen here. This concept also bridges to Solutions and Some Basic Concepts in Chemistry, so mastering it strengthens performance on linked questions from those topics as well. Plausibility check: 0.1 M KCl has a known conductivity near 0.0129 S cm^-1, matching the computed result and confirming the calculation.