What does this sign indicate?

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.