Which of the following is correct with regard to methemoglobin? Select one: a. It normally constitutes approximately 8% of total hemoglobin. b. It shifts theoxyhemoglobindisscociation curve to the right. c. It is less commonly found in infants. d. It is hemoglobin with the iron in the 3+ valence state. e. It is primarily reduced (in vivo) by ascorbic acid.