V. Reading Comprehension
         A polygraph machine, called a “lie detector,” is a common part of criminal investigation. This device is used to test how a person’s body reacts to questions. The theory behind it is that lying is of big stress and that this stress can be tested and recorded on a polygraph machine.
        When a person takes a polygraph test, four to six wires, called sensors, are attached to different parts of his or her body. The sensors pick up signals from the person’s blood pressure, pulse, and perspiration. Throughout the process of questioning, all the signals are recorded on a single strip of moving paper. Once the questions are finished, the examiner analyzes the results to determine if the person tested was being truthful.
         Well-trained examiners can usually detect lying with a high degree of accuracy when they use a polygraph. However, because different people behave differently when lying, a polygraph is by no means perfect.
【題組】41. Which of the following may be related to a polygraph, a lie detector?
(A) A parent and a newborn baby.
(B) A manager and a co-worker.
(C) A police officer and a thief.
(D) A principal and a teacher.