According to the law, a semi-trailer (which is part of an "articulated vehicle"):

1. AMust have stickers as well as strips on the rear panel of the semi-trailer.
2. BMust have two strips on the rear panel of the semi-trailer.
3. CMust have two reflective strips on which is written "Keep your distance".
4. DMust have stickers on the rear panel of the semi-trailer.

Pick an answer to test yourself