What differentiates a secondary alcohol from a tertiary alcohol?

A secondary alcohol is characterized by the structure of its carbon atom to which the hydroxyl group (-OH) is attached. In a secondary alcohol, the carbon holding the hydroxyl group is bonded to two other carbon atoms. This specific bonding arrangement is what establishes its classification as a secondary alcohol.

In contrast, a tertiary alcohol features the hydroxyl group attached to a carbon atom that is bonded to three other carbon atoms. Therefore, the main difference between secondary and tertiary alcohols lies in the number of carbon atoms that the carbon with the hydroxyl group is connected to. This structural distinction influences the physical and chemical properties of the alcohols in question.

The other options describe configurations that do not align with the definition of secondary alcohols. One option erroneously states that a secondary alcohol has the hydroxyl group on a carbon bonded to only one other carbon, while another implies excessive bonding to four other carbons, which is not possible for a secondary alcohol. Thus, the correct understanding centers on the bonding of the carbon to two other carbons, validating option C as the accurate choice.