Intermolecular hydrogen bonding occurs when hydrogen is directly bonded to a highly electronegative atom (like F, O, or N) and is attracted to another electronegative atom in an adjacent molecule.

Let's analyze each given compound:

• liq HF: Hydrogen is bonded to Fluorine (H-F). Fluorine is highly electronegative. Therefore, liq HF exhibits strong intermolecular hydrogen bonding.
• liq NH₃: Hydrogen is bonded to Nitrogen (N-H). Nitrogen is highly electronegative. Therefore, liq NH₃ exhibits strong intermolecular hydrogen bonding.
• CH₄: Hydrogen is bonded to Carbon (C-H). Carbon is not highly electronegative enough to form hydrogen bonds. Therefore, CH₄ does not exhibit intermolecular hydrogen bonding.
• CH₃OH: Hydrogen is bonded to Oxygen (O-H). Oxygen is highly electronegative. Therefore, CH₃OH exhibits strong intermolecular hydrogen bonding.
• N₂O₄: This molecule contains N-O bonds, but no hydrogen atoms are directly bonded to highly electronegative atoms (F, O, N). Therefore, N₂O₄ does not exhibit intermolecular hydrogen bonding.

Thus, intermolecular hydrogen bonding is expected in liq HF, liq NH₃, and CH₃OH. This is a total of three compounds.

Option Analysis:

• A) All: Incorrect, as CH₄ and N₂O₄ do not form hydrogen bonds.
• B) All leaving one: Incorrect, as two compounds do not form hydrogen bonds.
• C) Three: Correct, as liq HF, liq NH₃, and CH₃OH exhibit hydrogen bonding.
• D) None of these: Incorrect.

Correct Answer: (C)