How can you tell if you're turning the adjusting bolt in the correct direction?

The correct answer indicates that the slack adjuster pulls the pushrod out of the chamber when the adjusting bolt is turned in the appropriate direction. This is crucial because proper adjustment of the brake system is essential for maintaining effective braking performance. When the adjusting bolt is turned correctly, the slack adjuster mechanism engages to take up any slack in the brake system, which directly affects how effectively the brake shoes make contact with the brake drums. If the pushrod is being pulled out, it means that the slack adjuster is effectively functioning, indicating that you are turning the adjusting bolt in the right direction.

In contrast, the other options do not correctly indicate the effectiveness of adjusting the braking system. Activating the brake lights does not provide any information about the direction of the adjusting bolt; it's irrelevant to the adjustment process itself. If the adjusting bolt were to become loose, it would suggest improper adjustment rather than proper functioning. The camshaft rotating in the opposite direction does not relate to the adjuster's effectiveness or the direction of the adjusting bolt; it measures other aspects of the braking mechanism that do not directly indicate proper adjustment.