Select the correct answer. Which vitamin is an antioxidant?
vitamin A
vitamin C
vitamin D
vitamin B
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vitamin C

Explanation:

Ascorbic acid or vitamin C is a monosaccharide oxidation-reduction (redox) catalyst found in both animals and plants.[76] As one of the enzymes needed to make ascorbic acid has been lost by mutation during primate evolution, humans must obtain it from their diet; it is therefore a dietary vitamin.[76][77] Most other animals are able to produce this compound in their bodies and do not require it in their diets.[78] Ascorbic acid is required for the conversion of the procollagen to collagen by oxidizing proline residues to hydroxyproline.[76] In other cells, it is maintained in its reduced form by reaction with glutathione, which can be catalysed by protein disulfide isomerase and glutaredoxins.[79][80] Ascorbic acid is a redox catalyst which can reduce, and thereby neutralize, reactive oxygen species such as hydrogen peroxide.[76][81] In addition to its direct antioxidant effects, ascorbic acid is also a substrate for the redox enzyme ascorbate peroxidase, a function that is used in stress resistance in plants.[82] Ascorbic acid is present at high levels in all parts of plants and can reach concentrations of 20 millimolar in chloroplasts.