The polygraph test is used widely in a variety of circumstances. Generally, the results of a polygraph are not admissible in a criminal trial, but police can use it as an investigative tool. Additionally, some companies and government agencies use it as part of the job interview process, and some polygraph administrators have even suggested it be part of premarital counseling for engaged couples. Despite its prevalence, many people still have misconceptions about what the polygraph does and doesn't do. Which of the following physiological responses does the polygraph measure?

a. Rate of speech
b. Eye movement
c. Breathing
d. Facial expressions