Which of the following accurately pairs the type of receptor to the stimuli in which it responds?
a. chemoreceptor–pressure
b. photoreceptor–chemicals
c. pain receptor–tissue injury
d. mechanoreceptor–temperature

C. Pain receptor–tissue injury 

Neuroreceptors are found all over one's body and epithelial tissues to detect and be aware of the external stimuli
Receptor proteins are molecules inside a cell or on its surface on which ligands bind. A ligand is any substance (e.g. a hormone, drug, functional group) that binds specifically and reversibly to another chemical entity to form a large complex. Receptor proteins found inside a cell are called internal receptors or intracellular receptors or cytoplasmic receptors. 

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1. protection 2. homeostasis 3. storage4.blood formation5.bone marrow 6.movement