Which of the following indicates a problem if the clutch is not in during a safe start?

When performing a safe start in a vehicle, particularly in a commercial truck, pressing the clutch pedal is a crucial safety step. If the clutch is not engaged (pressed down) during this process, it can indicate that there's an issue preventing the vehicle from starting. This feature is designed to ensure that the vehicle does not inadvertently move during starting, which could lead to a dangerous situation.

Specifically, if the clutch is not in, the ignition system is designed to prevent the engine from starting as a safety precaution. This means that the clutch serves as a protective mechanism, allowing the operator to confirm that all systems are ready before the vehicle is transitioned into gear. In essence, if the truck does not start with the clutch pedal released, it is functioning as intended, highlighting a necessary procedure for safety.

The other options refer to issues that do not directly relate to the safe start mechanism. For example, lights functioning or brakes failing are independent of the clutch operation at the time of starting, and engine overheating is an issue that may arise during operation rather than during the initial starting process.