Which term describes a rabbit that is slim, alert, and active?

The term that best describes a rabbit that is slim, alert, and active is "racy." This word captures the essence of a rabbit that possesses an agile and sprightly demeanor, often associated with those that are finely built and energetic. A racy rabbit typically has a sleek body type and is characterized by its readiness and responsiveness to its surroundings, which is reflected in its active nature.

In contrast, other terms do not fit the description as accurately. "Robust" refers to strength and solidness, suggesting a heavier or bulkier build rather than the slimness associated with a racy rabbit. "Docile" denotes a calm and easy-going temperament, which does not align with the idea of being alert and active. Lastly, "shy" implies a lack of confidence or reticence, which contrasts with the lively and responsive characteristics of a racy rabbit. Thus, "racy" is the most appropriate choice to describe a rabbit that is slim, alert, and active.