What is a key feature of a fluid extract?

A fluid extract is characterized by having a higher potency than tinctures, which makes option B the correct choice. Fluid extracts are concentrated herbal preparations that are made by extracting the active constituents of a plant using a solvent, typically a combination of alcohol and water. This extraction process allows for the concentration of the plant's active ingredients, resulting in a product that is usually much stronger than tinctures.

While tinctures also use alcohol as a solvent, they tend to have a lower concentration of active components because they are often diluted to achieve a specific therapeutic effect. The higher potency of fluid extracts means that smaller doses can be used to achieve the desired effects, making them a preferred choice in situations where a strong herbal remedy is required.

Other options can be analyzed in relation to this fact: fluid extracts are not necessarily less concentrated than tinctures (which dismisses the first option), nor are they limited to only being water-based (as they typically include alcohol in their formulation). Additionally, fluid extracts do contain alcohol, which eliminates the possibility of them containing no alcohol. Thus, the key defining feature of fluid extracts is their higher potency compared to tinctures.