Acupuncture is an alternative medicine that uses wire-thin needles inserted by a trained practitioner into specific points in the body. this ancient form of pain relief and stimulation is said to benefit patients by blocking channels which practitioners claim allow pain to travel within the body. this practice became more widely recognized and used after a new york times reporter wrote in 1971 of a positive experience with it after surgery. those who doubt the effectiveness of this treatment for pain attribute the pain relief to a placebo effect: if a patient believes something will reduce their pain, they will experience some relief. the national institutes of health says that acupuncture relieves pain and reduces nausea and vomiting, although it is unclear how it works. the few adverse effects reported are due to improperly sterilized needles or improper delivery, making this still a fairly low risk option. for anyone considering acupuncture, they should first research its effectiveness for their specific condition. summary of statements published by the national institutes of health after reading the passage about acupuncture, identify which scientific claim explains why some people say acupuncture does not truly relieve pain.

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.