Which of the following amines exists as a gas at room temperature?

The correct answer is Option (4) → All of the above

Methylamine (\( \ce{CH3NH2} \)), ethylamine (\( \ce{C2H5NH2} \)) and dimethylamine (\( \ce{(CH3)2NH} \)) each have only one or two carbon atoms, so all three are lower aliphatic amines and are gases.

NCERT (2026-27 edition):
9.5 Physical Properties – “The lower aliphatic amines are gases with fishy odour. Primary amines with three or more carbon atoms are liquid and still higher ones are solid.”