What does this sign indicate?

What does this sign indicate?
A)The distance remaining to reach a stop sign.
B)That there is a hazard 4.25 kilometres ahead.
C)The length over which the hazard exists.Correct
This supplementary panel accompanies another danger or regulatory sign and indicates the length (duration) of the hazardous section or the section in which the regulation applies. When this panel does not display the two lateral arrows, it will indicate the distance to the beginning of the hazard or to the beginning of the regulation.