Which one of the following formula is used for calculation of base saturation

Answer: Option A

Base saturation is calculated as the percentage of CEC occupied by base cations. Base saturation is closely related to pH, as base saturation increases, pH increases. Soils with high percent base saturation have a higher pH, therefore they are more buffered against acid cations from plant roots and soil processes that acidify the soil.
Base saturation can be calculated by: $$\frac{\text{Total bases}}{\text{CEC}}\times 100$$
CEC is Cation exchange capacity.