When is overtaking prohibited in tunnels?

When is overtaking prohibited in tunnels?
A)When the tunnel is not lit.
B)When there is more than one lane for each direction.
C)When there is only one lane for each direction.Correct
Overtaking is prohibited in tunnels, underpasses and road sections affected by the 'Tunnel' sign where there is only one lane available for the direction of travel of the vehicle intending to overtake.