A nurse is caring for a client who is taking warfarin and reports taking several new herbal supplements. The nurse should identify that which of the following supplements is contraindicated for concurrent use with warfarin?

A. Ginkgo biloba can increase the risk of bleeding when taken with warfarin, as it has anticoagulant effects. B. Coenzyme Q10 has a mild anticoagulant effect but does not have a significant contraindication with warfarin. C. Valerian is generally safe with warfarin, although it may have sedative effects. D. Probiotics do not interact with warfarin and are safe to use concurrently.