Generalized anxiety disorder (GAD) is a mental disorder characterized by excessive worrying. Its symptoms include unproductive worrying, trouble stopping the worry process, worry about every part of daily life, and muscle tension and fatigue.

Flashbacks are one of the most prevalent symptoms of a different disorder—PTSD, or post-traumatic stress disorder. 

Although many children and adolescents may suffer from generalized anxiety disorder (GAD), it is generally not diagnosed until later in development. The other four choices are more frequently diagnosed in those under 18 years old.

Separation anxiety disorder is most common in young children, and is characterized by a consistent refusal to do things that require separation from loved ones. A common symptom is school refusal, which requires an intervention to be designed by a school-based mental health clinician (e.g., school psychologist).

The amygdala is the part of the brain that is most active when you experience fear, so it is especially active in people with anxiety disorders. As for the other answers, the cerebellum controls fine motor skills, the temporal lobe controls hearing and language, the basal ganglia directs intentional movements, and the pituitary gland releases hormones.

PTSD is an anxiety disorder characterized by flashbacks to stressful life events, such as service in a war. The answer choices "supportive home environment" and "healthy sexual relationships" are actually the opposite of two other common sources of PTSD-- child abuse and sexual assault. "Fear of a specific animal" is characteristic of a phobia and an "obsession that the environment is filled with dirty germs" is characteristic of OCD. 

Preparedness theory holds that some fears, such as snakes and spiders, are more common than others because those stimuli were serious threats to their ancestors. Therefore, people are innately, biologically predisposed to fear these things more than other things (i.e. phobias of snakes are more common than phobias of butterflies). Preparedness theory does not define what makes certain people more likely to develop phobias ("people are born prepared to develop phobias of certain things"); it merely explains why, overall, the human race is more afraid of some things than others. As for the other three answers, preparedness theory does not have to do with phobia treatment, phobias can be cured, and phobias do not help prepare someone for other fears.

Behavioral psychology is very focused on learned behaviors (conditioning) and would use the girl as an example of a learned phobia. If explaining a phobia, biopsychology would likely talk about chemicals in the brain, developmental psychology about parenting and lifespan factors, social psychology about interpersonal relationships, and psychodynamic psychology about unconscious conflicts. 

Claustrophobia is the fear of small, tight spaces, so someone with claustrophobia would likely not want to climb through a narrow cave. Agoraphobia is the fear of public spaces, arachnophobia is the fear of spiders, social phobia is the fear of social situations and embarassment, and mysophobia is the fear of germs and dirt.

Agoraphobia is the fear of being in places or situations from which escape might be difficult or embarrassing. In other words, it is the fear of open spaces.

Avoidance of what causes the anxiety is an overarching behavioral response that comes with anxiety disorders. For example, the behavioral response of avoidance in agoraphobia would be not going in to crowded places.