On a road with three lanes in each direction, when can you drive in the left lane?

On a road with three lanes in each direction, when can you drive in the left lane?
A)Only to overtake.
B)Never.
C)When the other lanes are occupied and it does not obstruct the vehicles travelling behind.Correct
On carriageways outside built-up areas with more than one lane reserved for our direction of travel, we will normally drive in the one on the far right, although we may use the others when traffic or road circumstances so advise, provided we do not impede the progress of vehicles following us.
With three or more lanes, lorries, vans and special vehicles with a MAM exceeding 3,500 kg, and combinations of vehicles longer than 7 metres, will travel in the right lane, being able to use the immediately adjacent one exceptionally, but never the others.