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Which one of the following is an example of negative feedback loop in humans?

A)  Secretion of sweat glands and constriction of skin blood vessels when it is too hot

B)  Constriction of skin blood vessels and contraction of skeletal muscles when it is too cold

C)  Secretion of tears after falling of sand particles into the eye

D)  Salivation of mouth at the sight of delicious food