In Carius method for halogens, a known mass of the organic compound is heated with fuming nitric acid in the presence of silver nitrate inside a sealed Carius tube. The halogen is oxidised and precipitated as silver halide, which is filtered, washed, dried, and weighed. The percentage of chlorine is calculated from %Cl = (atomic mass of Cl / molar mass of AgCl) x (mass of AgCl / mass of compound) x 100. The molar mass of AgCl is 108 + 35.5 = 143.5 g per mol. Substituting: %Cl = (35.5 / 143.5) x (0.12 / 0.15) x 100 = 0.2474 x 0.8 x 100 = 19.8%. The value 24.7% mistakenly drops the mass ratio (0.12/0.15) and reports only the elemental fraction times 100. The value 15.8% uses an incorrect molar mass for silver chloride. The value 35.5% simply quotes the atomic mass of chlorine without performing the gravimetric calculation. This relation follows the NCERT Carius halogen estimation. Plausibility check: chlorine forms a fraction of the silver chloride mass, so a value near 20% is reasonable for the given data, confirming the answer.