Although "lie detectors" are widely used by governments, police departments and businesses, the results are not always accurate. Lie detectors are commonly【C1】______as emotion detectors, for their aim is to【C2】______bodily changes that contradict what a【C3】______says. The lie detector records changes【C4】______heart rate, breathing, blood pressure, and the electrical【C5】______of the skin. In the first part of the【C6】______, you are electronically connected to the machine and【C7】______a few neutral questions("What is your name？" etc). Your physical reactions serve【C8】______the standard for evaluating what comes【C9】______. Then you are presented with a few【C10】______questions among the neutral ones("When did you rob the bank？" ). The idea is that if you are【C11】______, your body will reveal the truth, even if you try to【C12】______it. Your heart rate and breathing will change【C13】______as you respond to the question.
That is the theory, but psychologists have found that lie detectors are simply not【C14】______. Since most physical changes are the same across【C15】______emotions, lie detectors cannot tell【C16】______you are feeling angry, nervous or excited.【C17】______people may be tense and nervous【C18】______the whole procedure. They may react physiologically to a certain word("bank")not because they robbed it, but because they recently used a bad check. In either【C19】______, the machine will record a "lie" .
On the other hand, some practiced liars can lie【C20】______hesitation, so the reverse mistake is also common.
【C1】

A. fixed
B. designed
C. known
D. produced