An electrical impulse spreads through the ventricles via:

Patients receiving hemodialysis must go to a special center ________ time(s) a week for two to three hours at a time

a. one b. two c. three d. four

Which of the following pigmented lesions of oral mucosa is most commonly encountered in dental patients?

a. Freckles (ephelides) b. Intramucosal nevus c. Melanoma d. Amalgam tattoo e. Bismuth line