The police fortunately gained the key clew according to the foot mark in the ______ of the road.
【正确答案】 C
【答案解析】警察幸运地根据路上泥泞中的脚印获得了关键的线索。A．clay指做陶器用的“粘土” B．dirt“尘，土，污垢”C．mud“泥巴，稀泥” D．soil“土壤”