All metals except ............ exist as solid at room temperature.

Correct option is D

Mercury is the only metal that is liquid at room temperature. Its unique properties make it suitable for use in thermometers, barometers, and other instruments. Explanation of options: (a) ✘ Aluminium is solid and widely used in utensils, frames, etc. (b) ✘ Gallium melts near body temp but remains solid at room temp. (c) ✘ Indium is soft but remains a solid under room temperature. (d) ✔ Mercury stays liquid even at normal room conditions.