About Fog: why your normal driving habits no longer apply: which statement is WRONG?
In dense fog the normal two-second following distance is still sufficient.
Fog lights help others see you, but change nothing about your own reduced sight; you adjust your driving (speed, distance) regardless, once visibility is severely limited.
You follow the right-hand lane as much as possible, so that in an emergency you can use the hard shoulder as a direct escape route.
Referably do not overtake in dense fog, not even on a motorway.
Explanation
trap: a fixed rule of thumb applied without adjustment. Book p.191 - in very dense fog (visibility under 50 metres) three seconds, not two, applies