Ketones are reduced to the corresponding alcohols by catalytic hydrogenation to form:

Ketones are organic compounds that contain a carbonyl group (C=O) bonded to two carbon atoms. When ketones are subjected to catalytic hydrogenation, the carbonyl group is reduced to an alcohol functional group (C-OH). The resulting product depends on the structure of the ketone.

Explanation:

1. Catalytic Hydrogenation:
Catalytic hydrogenation is a chemical reaction in which hydrogen gas (H2) is used in the presence of a catalyst to reduce a compound. In the case of ketones, catalytic hydrogenation involves the addition of hydrogen (H2) across the carbon-oxygen double bond in the carbonyl group, resulting in the formation of an alcohol.

2. Reduction of Ketones:
When ketones undergo catalytic hydrogenation, the carbonyl group is reduced to an alcohol group. The double bond between the carbon and oxygen atoms is broken, and a hydrogen atom is added to each of the carbon and oxygen atoms.

3. Formation of Secondary Alcohols:
The reduction of ketones leads to the formation of secondary alcohols. A secondary alcohol is an alcohol in which the carbon atom bonded to the hydroxyl group (OH) is also bonded to two other carbon atoms. This is because the carbon atom in the ketone that is reduced is bonded to two other carbon atoms.

4. Examples:
Let's consider the example of acetone, which is a commonly known ketone. The reduction of acetone by catalytic hydrogenation results in the formation of isopropanol, a secondary alcohol. The reaction can be represented as follows:

CH3COCH3 + H2 → (Pt catalyst) → CH3CHOHCH3

Another example is the reduction of propanone (acetone) which results in the formation of propan-2-ol (isopropyl alcohol):

CH3COCH3 + H2 → (Pt catalyst) → CH3CHOHCH3

Conclusion:
In conclusion, when ketones are subjected to catalytic hydrogenation, they are reduced to the corresponding alcohols. Specifically, ketones are reduced to secondary alcohols, where the carbon atom bonded to the hydroxyl group is also bonded to two other carbon atoms. Therefore, the correct answer is option 'C' - secondary alcohols.