单选题 While researchers may not ______ the expansive claims of hard-core vitamin enthusiasts, evidence suggests that the nutrients play a much more complex role in assuring vitality and optimal health than was previously thought.

【正确答案】 D
【答案解析】authorize批准；license许可，特许；counteract抵消，阻碍；endorse在(票据)背面签名，正式赞同或支持。研究者没有支持那些顽固的维他命狂热者，所以选D。