Anxiety disorders physically manifest as:

Anxiety disorders are characterized by heightened levels of arousal and nervousness, which are primarily associated with the activation of the sympathetic nervous system. This part of the autonomic nervous system is responsible for the body's "fight or flight" response, leading to physical symptoms such as increased heart rate, rapid breathing, sweating, and heightened alertness. These symptoms reflect a state of heightened physiological arousal that is often observed in individuals experiencing anxiety, making it the most accurate representation of how anxiety disorders physically manifest.

The other options reflect various human behaviors and responses but do not accurately capture the physiological manifestations of anxiety disorders. Social withdrawal can be a behavioral response to anxiety but does not directly represent a physical manifestation. Extreme happiness is not a characteristic of anxiety disorders, as they are defined by distress rather than positive emotions. Chronic fatigue may arise as a consequence of anxiety or from other factors but does not specifically indicate the physical manifestations associated with anxiety disorders themselves.