Which of the following will cool quickly

Question

$(a)\;\text{A polished metallic vessel filled with water at $100^{\circ}$ C} \\(b)\;\text{Polished metallic vessel filled with oilat $100 ^{\circ}C$ } \\(c)\;\text{A blackened metallic vessel filled with water at $100 ^{\circ}C$ } \\(d)\;\text{A blackened metallic versel filled with oil at $100^{\circ}$ C }$