Which one of the following is solid at room temperature?

The correct answer is Option (1) → CHI₃

Haloalkanes are held together by dipole–dipole and van der Waals forces, which grow stronger as the molar mass increases. So their physical state depends on their size: the lowest members are gases at room temperature, and the higher members are liquids or solids.

\( \ce{CH3Cl} \), \( \ce{CH3Br} \) and \( \ce{C2H5Cl} \) are among the lowest members and are gases at room temperature, while iodoform, \( \ce{CHI3} \), with a much larger molar mass (394 g mol⁻¹), is a yellow crystalline solid.

So the compound that is solid at room temperature is CHI₃ (iodoform).

NCERT (2026-27 edition):
Physical Properties – …