Select the compound from the following that will show intramolecular hydrogen bonding.

Intramolecular hydrogen bonding occurs within the same molecule and requires a hydrogen bond donor and acceptor to be positioned close to each other. Intermolecular hydrogen bonding occurs between different molecules.

$$H_2O$$, $$NH_3$$, and $$C_2H_5OH$$ contain hydrogen-bonding groups, but they do not have suitably positioned donor and acceptor sites within the same molecule. Therefore, they exhibit intermolecular hydrogen bonding.

In $$o$$-nitrophenol, the $$-OH$$ group and $$-NO_2$$ group are present at adjacent (ortho) positions on the benzene ring. The hydrogen atom of the $$-OH$$ group forms a hydrogen bond with an oxygen atom of the $$-NO_2$$ group within the same molecule.

This interaction results in the formation of a stable six-membered pseudo-ring through intramolecular hydrogen bonding.

Therefore, $$o$$-nitrophenol is the only compound among the given options that exhibits intramolecular hydrogen bonding.

Hence, the correct answer is:

$$o\text{-nitrophenol}$$