Which one of the following non-metals is liquid?

Concept: At standard room temperature (around 25°C, normal atmospheric pressure), every element is solid, liquid, or gas depending on where this temperature falls relative to its melting point and boiling point. Among all elements, only two are liquid under these ordinary conditions: mercury (a metal) and bromine (a non-metal); every other common non-metal is solid or gas at room temperature.

Application: Iodine is a violet-black crystalline solid that sublimes into a violet vapour; sulfur is a pale yellow crystalline solid; phosphorus exists as solid allotropes (white, red, or black). Bromine, by contrast, is a reddish-brown liquid at ordinary room temperature.

Cross-check: comparing melting and boiling points confirms this:

Since 25°C falls between bromine's melting point (-7.2°C) and boiling point (58.8°C), bromine is a liquid — the only liquid non-metal among the given options. Hence, Bromine is the correct answer.