After adding two half reactions in ion electron method:

Explanation

The ion-electron method, also known as the half-reaction method, is a systematic approach to balancing redox reactions. It involves splitting the reaction into two half-reactions-one for oxidation and one for reduction. Each half-reaction is separately balanced for both atoms and charge before being combined to form a balanced overall reaction. Option A is correct because charge conservation is a fundamental principle in balancing redox reactions. Option B is correct because balancing the number of atoms is necessary in chemical reactions. Option C is incorrect because balancing the total number of ions is not a required step in this method. Option D is correct as both A and B are true statements regarding the ion-electron method.