What does this sign mean?

Why this is the correct answer

Prohibition of driving at a speed greater, in kilometres per hour, than that indicated on the sign. It applies from the place where the sign is situated up to the next "End of speed limit" sign, "End of prohibitions" sign or another "Maximum speed" sign, unless it is placed on the same post as a warning sign or on the same panel as that sign, in which case the prohibition ends when the danger indicated ends. When placed on a non-priority road, it ceases to apply when leaving a junction with a priority road. If the limit indicated by the sign coincides with the maximum speed permitted for that type of road, it serves as a general reminder of the prohibition on exceeding it.