Which of these is a physical symptom of stress?

Irregular heartbeats are a recognized physical symptom of stress due to the body's response to perceived threats or challenges. When a person experiences stress, the body activates the sympathetic nervous system, leading to the release of stress hormones such as adrenaline and cortisol. This physiological response can result in various effects on the cardiovascular system, including an irregular heartbeat, rapid heart rate, or palpitations.

In contrast, the other options—such as increased creativity, heightened alertness, and emotional stability—are not physical symptoms. Instead, they may reflect cognitive or emotional responses to stress. Heightened alertness, for instance, is more of a mental state indicating preparation for action rather than a direct physical manifestation.