Which of the following signals denotes a 'STOP'?

The signal that denotes a 'STOP' includes a solid red light, a red arrow, and a flashing red light. Each of these signals conveys a clear instruction to drivers that they must come to a complete stop.

A solid red light indicates that vehicles must stop and can only proceed when it is safe and the light changes to green. Similarly, a red arrow points to a specific direction (depending on the arrow's orientation) where stopping is required. A flashing red light functions similarly to a stop sign, indicating that vehicles must stop before proceeding, ensuring that they yield to any pedestrians or oncoming traffic before proceeding.

The other options do not provide the same clear instruction to stop. A green light combined with a stop sign does not denote stopping—as a green light generally means go, therefore creating confusion regarding the stop sign. A flashing yellow light indicates caution and that drivers should slow down and prepare to stop if necessary, but it does not require a full stop. A solid yellow light signals that a red light is imminent, warning drivers to prepare to stop, but it does not instruct a stop in itself.