Given below are two statements
Statement I: The permanent negative charges result from the isomorphous substitution.
Statement II: The permanent negative charges result from exposed crystal edges.
In light of the above statements, choose the correct answer from the options given below:

Correct option is C

Permanent negative charges in soils primarily result from isomorphous substitution, where one ion is replaced by another of similar size but different charge (e.g., Al³⁺ replacing Si⁴⁺). This occurs within the clay mineral lattice. The idea that permanent charge comes from crystal edges is incorrect—it is edge charges that are variable, not permanent.