You Find That the CEC of a Sandy Loam Soil

You find that the CEC of a sandy loam soil at pH 5.0 is 8 cmol_c/kg and at pH 8.2 it is 14 cmol_c/kg.What is the most likely reason for this difference?

A) increase in the pH-dependent charges on 2:1 type silicate clays
B) removal of Al³⁺ ions from the exchange complex at higher pH.
C) ionization of carboxyl and phenolic groups to release H⁺ ions
D) removal of Al atoms from tetrahedral layers at low pH.
E) replacement of trivalent Al³⁺ ions with divalent Ca²⁺ ions at high pH.