What does this sign indicate?

A)One-way road, driving in the opposite direction is prohibited.Correct
B)Obligation to continue straight ahead.
C)Two-way road.
The sign indicates that the road is one-way. This sign allows changing direction; what is prohibited is changing the direction of travel (U-turn).
Do not confuse with the following circular sign, which obliges you to continue straight ahead, prohibiting all other manoeuvres.
Do not confuse with the following circular sign, which obliges you to continue straight ahead, prohibiting all other manoeuvres.