What lighting must be on a tractors trailer during lighting-up hours?

Indicators, brake lights, rear number plate light, red reflectors and rear tail lights.
Indicators, two white or yellow headlamps and rear number plate lights only.
An unloading light.
Brake lights and indicators only.

Explantion: A trailer being towed by a tractor must have rear indicators, brake lights, a rear number plate light, red reflectors and rear tail lights whilst being towed on a public road.

Theory Tester

What lighting must be on a tractors trailer during lighting-up hours?

Legal Matters/Rules of the Road