Sodium adsorption ratio (SAR) can be calculated by using of formula

Answer: Option B

Sodium adsorption ratio is a measure of the amount of sodium (Na) Relative to calcium (Ca) and Magnesium (Mg) in the water extract from saturated soil paste. It is the ratio of the sodium concentration divided by the square root of one-half of the calcium and magnesium concentration.
It can calculated by using formula: $$\text{SAR}=\frac{\text{N}{\text{a}}^{+}}{{\left[\left(\frac{\text{C}{\text{a}}^{2+}+\text{M}{\text{g}}^{2+}}{2}\right)\right]}^{0.5}}$$