In which examples does a vitamin or mineral function as a cofactor?
A. Hydroxylase enzymes require vitamin C during collagen synthesis.
B. Calcitriol, a form of vitamin D, regulates calcium levels in blood.
C. Ribosomes require phenylalanine to construct proteins.
D. DNA polymerase requires zinc to replicate DNA.

A -Hydroxylase enzymes require vitamin C during collagen synthesis.

Explanation:

Vitamin C is essential for synthesis of collagen. Vitamin C is the essential cofactor for the two enzymes required for collagen synthesis which are  prolyl hydroxylase (to stabilize the collagen molecule) and lysyl hydroxylase (to give structural strength cross-linking).

In addition to its antioxidant functions, vitamin C regulates the synthesis of the structural protein collagen. The role of vitamin C in the hydroxylation of collagen molecules is well characterized. Hydroxylation of collagen is necessary for its extracellular stability and support of the epidermis.

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explanation: