What does a white sign with a red circle and a line through it indicate?
Answer: B — No entry or do not enter.
A white sign with a red circle and a line through it typically indicates the prohibition of a certain action. Option A and D are incorrect as they specify specific actions of "parking" and "U-turn", whereas option C is incorrect as it specifies a specific direction of "left". The only option that correctly describes the general meaning of the sign is option B, which signifies a prohibition.