About Lighting and reflection of the trailer: which statement is correct?

A trailer only needs a fog light if it was put into service after 31 December 1997.

If the trailer's reflectors are clean, you are visible enough even without the trailer lights on.

Extra marker lights are required if the trailer is longer than 6 metres and/or wider than 2,10 metres.

The white retroreflectors of a trailer belong at the rear.

Explanation

Book p.232 - extra marker lights are required if the trailer is longer than 6 metres and/or wider than 2,10 metres.