Final answer:
The polygraph assumes that lying will produce noticeable physiological responses such as increased heart rate and sweating. However, its reliability is debatable since there's no unique physiological response to lying, and many factors can influence the results of a polygraph test.
Step-by-step explanation:
The underlying assumption on which the polygraph is based is that people feel nervous when they lie, which manifests in physiological reactions such as increased heart rate, respiration rate, and sweating (answer d). A polygraph test, or lie detector test, measures these physiological responses as individuals answer a series of questions, on the presumption that dishonest answers will be associated with increased levels of arousal.
However, the accuracy and validity of polygraphs remain contentious; critics point out that no specific pattern of physiological arousal is exclusively linked to lying. Emotional responses to questions can elevate arousal due to factors other than dishonesty, and some individuals may not exhibit significant physiological changes even when lying. Consequently, the reliability of polygraph tests is highly questionable, and legal systems and psychologists continue to debate their usefulness and ethical implications.