An unsafe condition is a latent or system-level issue that increases the risk of errors or harm, often existing before an incident occurs. It is distinct from active errors or outcomes.

Option A (A mislabeled specimen discovered in the laboratory): This is an active error that has already occurred, not an underlying condition. It is a result of an unsafe process but not the condition itself.

Option B (A high healthcare-associated infection rate): This is an outcome, not a condition. It reflects the result of multiple factors (e.g., poor hand hygiene) rather than a specific unsafe condition.

Option C (An incorrectly marked surgical site identified before surgery): This is an active error caught before harm, not a latent condition. It indicates a failure in process but is not the condition predisposing to the error.

Option D (Similarly named medications stored in proximity to each other): This is the correct answer. NAHQ CPHQ study materials define unsafe conditions as system vulnerabilities, such as storing look-alike/sound-alike medications together, which increases the risk of medication errors. This aligns with Joint Commission and ISMP guidelines on medication safety.