Select the correct option to test your answer:
Correct Answer: Option D ($${\text{ESR}} = \frac{{{\text{Exchangeable}}\,{\text{N}}{{\text{a}}^ + }}}{{{\text{Exchangeable}}\left( {{\text{C}}{{\text{a}}^{2 + }} + {\text{M}}{{\text{g}}^{2 + }}} \right)}}$$)
Verified correct option for Agriculture (Soil Science).