Is the U-turn made by the red vehicle correct?

A)Yes, because it is performed in a single manoeuvre.
B)No, because it obstructs the vehicles following it.Correct
C)Yes, because there is a broken line.
When making a U-turn we must choose a suitable place so that the road is blocked for the shortest time possible without obstructing other users. If your presence on the carriageway obstructs vehicles travelling behind you, you must leave it on its right side, if possible, until you can carry it out, and if there is no possibility, you must refrain from making the U-turn and look for a suitable place further ahead.