May you make a left turn at an intersection signposted in this way?
A)Yes.Correct
B)No.
The sign in the question indicates that, on the road that continues in the direction of the arrow, vehicles must travel in the direction indicated by it, and that travel in the opposite direction is prohibited. This sign does not prohibit changing direction.
Do not confuse it with the mandatory sign "compulsory direction" (round sign), which prohibits changing direction and the direction of travel.