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.

Increased salivation is not a physiological response to anxiety. The other four choices are examples of physiological responses that are commonly caused by anxiety.

Liz frequently experiences unexpected periods of intense fear and discomfort accompanied by increased heart rate and respiration, shakiness, sweating, and fear of losing control. These are the symptoms of a panic attack. Panic can be defined as an extreme sense of fear with an extreme stress response. Panic attacks are periods in which the person feels extreme fear and discomfort and may experience a pounding heart, shortness of breath, shakiness, and sweating. Many times, the person is also afraid that they will lose control. A panic disorder is characterized by frequent, unexpected panic attacks and social limitations to avoid the onset of such attacks.

Taijin kyofusho refers to a culture specific social anxiety in Korea and Japan. A person with social anxiety in these cultures is most likely going to fear that their body odor or the act of blushing will be offensive to others.

"GABA" (Gamma-Amino Butyric Acid) is an inhibitory neurotransmitter, and is found throughout the neurons of the cortex. GABA deficiencies have been linked to anxiety disorders, and some anxiolytics (anxiety medications) work by increasing quantities of GABA available at neuron receptor sites.

The other choices are incorrect. "Serotonin" is primarily associated with regulating mood, appetite, and sleep, and is also implicated in nociception (sensation of pain). This neurotransmitter plays a major role in depression, but not necessarily anxiety. "Dopamine" is a major component of the reward system, and plays a role in arousal, motivation, motor control. "Norepinephrine" is mainly involved in preparing the body for action, for instance the 'flight or fight' response. It increases vigilance and alertness, focuses attention and improves memory recall and formation. Raised levels of norepinephrine can result in anxiety by way of increased stress. Last, "acetylcholine" is associated with motor neurons, and provides signals for the body to contract muscles. Drugs affecting this neurotransmitter thus may lead to paralysis or convulsions. In the brain acetylcholine plays a role in attention, arousal, and motivation.