which of the control lights visible in the illustration informs you that direction indicators are enabled?

The illustration shows three warning lights: A - green arrows to the left and right, B - a green sidelight symbol, C - an orange headlamp with rays crossed by a wavy line, that is, the rear fog light. Light A shows that the indicators are on - answer A.

The arrows are the only one of these warning lights that is designed to flash: the Regulation on the technical conditions of vehicles requires a control signal showing that the indicators are working in the form of a flashing green light, a sound signal or both at once, and the indicators themselves must flash at a frequency of 90 cycles per minute with a permitted deviation of 30. The green symbol B and the orange C are lit continuously - they are signals that the lights are switched on. The wavy line on symbol C means fog, and the rays on the right side of the lamp indicate a rear light; its warning light has a yellow warning colour, and the light itself may be switched on only when visibility is less than 50 m, and you must remember to switch it off when the fog clears. You use the indicator before every change of direction and lane, and when the arrow flashes twice as fast as usual, you check the bulbs.

Legal basis: Annex No. 6 to the Regulation on the technical conditions of vehicles and the scope of their necessary equipment; Art. 22 para. 5 and Art. 30 para. 3 of the Road Traffic Act (Prawo o ruchu drogowym)