Which of the following causes vehicle fires from fuel?

The correct answer addresses the action of smoking while driving, which can easily ignite combustible materials inside or outside the vehicle if a flame comes in contact with flammable fuel vapors. Smoking creates an immediate fire hazard, especially if the driver is discarding cigarette butts or there are existing fuel leaks, as even a small spark can result in a fire.

In contrast, loose electrical connections can lead to short circuits, which may cause electrical fires but not directly link to fuel ignition. Poor ventilation primarily involves air flow and doesn't directly relate to fuel fires, although it can exacerbate existing fire situations. Neglecting to change oil could result in engine lubrication issues or excessive heat but is not a direct ignition source like a lit cigarette.