Who must wear a high-visibility vest with reflective elements during a motorcyclists' training session?
Explanation
During training, both the learner — marked with an "M" sign — and the driving instructor escorting them on a motorcycle (marked "DRIVING INSTRUCTOR") must wear a high-visibility vest.
KET reference: KET 26 p.: during training the learner must wear a high-visibility reflective vest bearing the distinguishing sign „M“; the instructor escorting them on a motorcycle must wear the same vest.