填空题 Fear is a normal, legitimate response to genuine danger. However, when fear spirals out of control, becoming persistent and irrational, it constitutes a phobia. Phobias affect a significant portion of the American population. Some experts believe that nearly twenty-five percent of Americans live with irrational fears that prevent them from performing everyday activities. Phobias, like other anxiety disorders, can greatly affect quality of life. Generally defined as an unrelenting, anomalous, and unfounded fear of an object or situation, a phobia is normally developed from a past negative experience or encounter. Children might adopt phobias by observing a family member"s reaction to specific stimuli. There is also data to suggest genetic factors linked to phobias.

多选题 It can be inferred from the passage that theories about phobias contain which of the following elements?

填空题 Select the sentence that explains the difference between normal fear and phobia.