.  Fear is often a     11    emotion. When you become frightened, many physical changes occur within your body. Your heartbeat and     12    quicken; your pupils expand to admit more light; large quantities of energy-producing adrenaline (肾上激素) are poured into your bloodstream.     13    a fire or an accident, fear can     14    life-saving flight. Similarly, when a danger is psychological rather than physical, fear can force you to take self-protective measures. It is only when fear is disproportional to the danger     15    that it becomes a problem.
    Some people are simply more vulnerable     16    fear than others. A visit to the newborn nursery of any large hospital will demonstrate that, from the moment of their births, a few fortunates respond calmly to sudden fear-producing situations such as a loudly slammed door. Yet a neighbor in the next bed may cry out with profound fright. From birth, he or she is more     17    learn fearful responses because he or she has inherited a tendency to be more     18    .
    Further, psychologists know that our early experiences and relationships strongly     19    and determine our later fears. A young man named Bill, for example, grew up with a father who regarded each adversity as a     20    obstacle to be overcome with imagination and courage. Using his father as a model, Bill came to welcome adventure and to trust his own ability to solve problems.11.