The correct answer is: A. Between the adjoining faces of the running rail and the check rail near the crossing.
Flange-way clearance is the distance between the adjoining faces of the running rail and the check rail near the crossing. It is important to ensure that this distance is adequate to allow the flanges of the wheels to pass through without derailing.
Option B is incorrect because it refers to the distance between the gauge faces of the stock rail and the tongue rail. This distance is known as the gauge. The gauge is the distance between the inside faces of the rails on a track. It is important to ensure that the gauge is correct to allow the wheels of the train to pass through without derailing.
Option C is incorrect because it refers to the distance through which the tongue rail moves laterally at the toe of the switch. This distance is known as the tongue rail movement. The tongue rail movement is the distance that the tongue rail is allowed to move laterally at the toe of the switch. It is important to ensure that the tongue rail movement is correct to allow the train to switch tracks without derailing.
Option D is incorrect because it is not a valid option.