The correct answer is: Only (ii) is correct.
The main reinforcement in the toe of a T-shaped R.C. retaining wall is provided on the top face perpendicular to the wall. This is because the main reinforcement needs to resist the bending moment that is generated at the toe of the wall due to the load from the soil. The bending moment is maximum at the toe of the wall, and it acts in a counterclockwise direction. The main reinforcement is therefore provided on the top face perpendicular to the wall so that it can resist the bending moment.
The other options are incorrect because they do not provide the main reinforcement with the necessary strength to resist the bending moment. The reinforcement on the bottom face of the wall is not effective in resisting the bending moment because it is not in tension. The reinforcement on the top face parallel to the wall is not effective in resisting the bending moment because it is not in compression.