(c) Mercury and Bromine
Mercury is a metal that exists as a liquid at room temperature. Bromine is a non-metal that exists as a liquid at room temperature.
The textbook explicitly states: "Metals are solids at room temperature, except mercury which is a liquid" and "The non-metals are either solids or gases except bromine which is a liquid." These two facts are standard exam points from Chapter 3. Remember: mercury = liquid metal; bromine = liquid non-metal. Options (a) and (d) are reversed, and (b) incorrectly lists iodine (a solid non-metal) instead of bromine.