Which of the following is a metal?

The correct answer is Option (2) → Mercury

Metals are usually shiny and good conductors of heat and electricity. Mercury is a metal, the only one that is liquid at room temperature, which is why it was used in thermometers.

Carbon, sulphur and iodine are non-metals: as solids they are dull or brittle and do not conduct heat and electricity well (graphite, a form of carbon, is the one non-metal that conducts electricity).