Dynamic equilibrium in a reversible reaction occurs when:

Dynamic equilibrium in a reversible reaction is reached when the rate of the forward reaction equals the rate of the reverse reaction. This means that the concentrations of reactants and products remain constant over time, even though both reactions continue to occur. In this state, the system is stable because the processes are balancing each other out, which allows for a dynamic state where changes can happen, but the overall concentrations do not change.

The other options do not accurately describe dynamic equilibrium. For instance, if the reactants were completely converted to products, it would indicate that the reaction has reached completion, not an equilibrium state. Similarly, stating that the concentration of reactants is greater than that of products does not reflect an equilibrium condition, as equilibrium can exist regardless of the relative concentrations, provided the forward and reverse reaction rates are equal. Thus, option B effectively captures the essence of dynamic equilibrium in reversible reactions.