Who has priority at unmarked crossroad?

Answer: B — no one

At an unmarked crossroad, there are no traffic signs or signals indicating which vehicle has priority. Therefore, all vehicles must yield to one another and proceed with caution. A and C may seem like logical options, but size and direction of travel do not determine priority in this scenario. Choosing D, the fastest vehicle, could also lead to reckless driving and potential accidents. Thus, the correct answer is B, as no one has priority at an unmarked crossroad.