A nurse is assisting with the preparation of an educational program about the use of oral contraceptives. The nurse should include that which of the following herbal supplements reduces the effectiveness of oral contraceptives?

A. Ginger root is not known to reduce the effectiveness of oral contraceptives significantly. B. St. John's wort is an herbal supplement that can induce the cytochrome P450 enzyme system, leading to increased metabolism of oral contraceptives and potentially reducing their effectiveness. Women taking oral contraceptives should be cautioned against using St. John's wort or advised to use alternative contraceptive methods. C. Gingko biloba is not known to reduce the effectiveness of oral contraceptives significantly. D. Glucosamine is not known to reduce the effectiveness of oral contraceptives significantly.