Which of the following liquid medications contains alcohol as a solvent?

The correct answer is tincture because it specifically refers to a medicinal extract that is prepared by soaking plant or animal material in alcohol or another solvent. In pharmacology, tinctures are commonly used for their ability to extract and preserve the active ingredients from the source material, which may contain useful therapeutic properties.

In contrast, aqueous suspensions are mixtures of solid particles suspended in water and do not typically contain alcohol. Syrups are concentrated solutions of sugar in water, often formulated with flavoring and medicinal agents, but they do not contain alcohol as a solvent. Lozenges are solid dosage forms meant to dissolve in the mouth and usually contain sweeteners and flavoring agents but lack alcohol as a solvent.

The defining characteristic of a tincture is its alcohol content, making it the most suitable choice in this context.