Which of the following is a sign of cardiac arrest in a donor?

Shortness of breath is a significant sign of cardiac arrest in a donor. During a cardiac arrest, the heart stops pumping effectively, which leads to decreased oxygen supply to the body's organs, including the lungs. This lack of oxygen can cause a donor to experience severe shortness of breath or difficulty breathing. It can be a result of the body’s attempt to get more oxygen when the heart is unable to circulate blood properly. Recognizing this symptom is crucial, as it can indicate that immediate medical intervention is necessary to address the underlying issue of cardiac arrest.

The other options, while they could pertain to various health conditions, do not specifically indicate cardiac arrest in a donor. Nausea, rash, and visual disturbances can arise from numerous causes, but they are not direct indicators of the critical situation represented by cardiac arrest. In a medical emergency, recognizing the correct signs is key for timely treatment and intervention.