Hydrogenation of unsaturated oils to semi-solid margarine Steps:

• Vegetable oils contain unsaturated fatty acids with carbon-carbon double bonds, making them liquid with low viscosity.
• To produce margarine, partial hydrogenation adds hydrogen gas (with a catalyst) across some double bonds.
• This increases saturation, straightening fatty acid chains and raising the melting point.
• The product becomes a semi-solid spread with higher viscosity than the original liquid oil.

Why C is correct:

• Hydrogenation saturates double bonds per the reaction: C=C + H₂ → CH-CH, increasing intermolecular forces and viscosity as defined by resistance to flow in fats.

Why the others are wrong:

• A: Hydrogen is added, but viscosity increases due to solidification, not decreases.
• B: Hydrogen is added during hydrogenation, not removed; viscosity also increases.
• D: Hydrogen is added, not removed.

Final answer: C