Which of the following is a sign of a heart attack?

Chest pain or discomfort that may spread to the jaw, shoulders, or arms is a classic and critical sign of a heart attack. This symptom is commonly associated with the condition because it reflects the heart's distress and can signal that the heart muscle is not receiving enough oxygen due to blockage in the coronary arteries. The pain may not be localized and can radiate to other areas, which helps to differentiate a heart attack from other types of discomfort.

While excessive sweating, nausea, and shortness of breath can occur during a heart attack, they may not be as definitive or specific as the chest pain or discomfort. These other symptoms may also manifest in various conditions, which means they are considered less characteristic when diagnosing a heart attack. Thus, the presence of chest pain or discomfort is particularly significant and provides a clearer indication of a potential heart attack situation that requires immediate medical attention.