Answer:
three types of stimuli—mechanical, thermal, and chemical; some endings respond primarily to one type of stimulation, whereas other endings can detect all types. Chemical substances produced by the body that excite pain receptors include bradykinin, serotonin, and histamine."
Explanation:
From edge
we have 300+300+50+350=1000 individuals
400 have the u2 gene
that means 40% or a frequency of 0.4