In ethanol, the attractive forces between adjacent molecules are

Step 1: Analyze the question The question asks about the forces between adjacent ethanol molecules (intermolecular forces), not the bonds within a molecule.

Step 2: Explain the concept

• Covalent bonds hold atoms together inside a molecule (intramolecular). They are not the attractive forces between molecules, so option A is out.
• Van der Waals (London dispersion) forces exist between all molecules. They come from temporary and induced dipoles.
• Hydrogen bonding occurs when hydrogen is bonded directly to a highly electronegative atom (N, O or F), and is attracted to a lone pair on a neighbouring molecule's N, O or F atom.

Step 3: Apply to ethanol Ethanol is CH₃CH₂OH.

• It has an -OH group, so hydrogen bonding occurs between the H of one molecule and the O of another.
• It also has an ethyl group (CH₃CH₂–), a non-polar hydrocarbon part. The molecules therefore also experience Van der Waals (dispersion) forces, which exist in every molecule.

So ethanol molecules attract each other through both hydrogen bonding and Van der Waals forces.

Step 4: Eliminate the options

• A. Wrong: covalent bonds are intramolecular.
• B. Wrong: "only" ignores the Van der Waals forces that are always present.
• C. Correct: both forces are present.
• D. Wrong: it ignores the hydrogen bonding from the -OH group.

Tip: Van der Waals forces are present in all molecules. If a molecule also has O-H, N-H or F-H, add hydrogen bonding. Watch for the word "only" in options, as it is often a trap. This also explains why ethanol (boiling point about 78 °C) boils much higher than dimethyl ether, which has no hydrogen bonding.