89. Which of the following statement is true about [ipoic acid? (A) It contains one disulfide group in its reduced form and two sulfhydryl groups in its oxidized form. (B) It contains one disulfide group in its oxidized form and two sulfhydryl groups in its reduced form. (C) It contains two disulfide groups in its reduced form and one sulfhydiyl group in its oxidized form. (D) It contains two disulfide groups in its oxidized fonn and one sulfliydiyl group in its reduced form. (E) None of the above.