Which of the following is one of the forms of anxiety?

Post-Traumatic Stress Disorder (PTSD) is indeed classified as a form of anxiety. It is a mental health condition that can be triggered by experiencing or witnessing a traumatic event. Individuals with PTSD often experience symptoms such as flashbacks, severe anxiety, and uncontrollable thoughts about the event.

The association of PTSD with anxiety stems from how individuals may react emotionally and psychologically to trauma, resulting in heightened states of arousal or anxiety, which can adversely affect their daily functioning. By understanding PTSD in the context of anxiety, one recognizes that it encompasses a range of symptoms that reflect the distressing effects of trauma on an individual's mental health.

In contrast, the other options provided do not fit the classification of anxiety disorders in the same way. Chronic Fatigue Syndrome relates more to persistent fatigue and physical symptoms, insomnia focuses primarily on sleep difficulties, and social isolation disorder is not formally recognized as a distinct anxiety disorder but rather describes a situation that may contribute to various mental health issues.