Cesium chloride density gradient centrifugation is commonly used for the separation of DNA molecules. The buoyant density, ρ, of a double stranded Cs⁺ DNA is given by the equation ρ = 1.66 + 0.098 X_{G + C}, where X_{G + C} denotes

A. Total number of G and C

B. Mole fraction of G + C

C. Number of GC repeats

D. Ratio of G + C to A + T content

Answer: Option B