A metal and a non-metal that exists in liquid state at the room temperature are respectively :

Elements exist in different physical states (solid, liquid, gas) at room temperature.

• Option (c) is correct because Mercury ($\mathrm{Hg}$) is the only metal that is liquid at room temperature, and Bromine ($\mathrm{Br}$) is a non-metal that exists as a reddish-brown liquid.
• Option (a) is incorrect because it lists the non-metal first, whereas the question asks for the metal first.
• Option (b) is incorrect because Iodine is a lustrous solid non-metal at room temperature.
• Option (d) is incorrect because Iodine is solid and the order is reversed.