The correct answer is: C. both (A) and (B).
Gauge tie plates are used to ensure the exact gauge of the track. They are placed at the toe of the switch and the nose of the crossing. The toe of the switch is the point where the rails diverge, and the nose of the crossing is the point where the rails meet. Gauge tie plates help to keep the rails in alignment and prevent them from spreading or shifting.
Option A is correct because gauge tie plates are placed at the toe of the switch. The toe of the switch is the point where the rails diverge, and the gauge tie plates help to keep the rails in alignment and prevent them from spreading or shifting.
Option B is correct because gauge tie plates are placed at the nose of the crossing. The nose of the crossing is the point where the rails meet, and the gauge tie plates help to keep the rails in alignment and prevent them from spreading or shifting.
Option C is the correct answer because it includes both Option A and Option B.
Option D is incorrect because it does not include both Option A and Option B.