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【单选题】
维生素 E 是抗氧化剂,能够清除体内的自由基。于是,保健品商家把维生素 E 作为提高免疫力、抗癌、抗衰老的灵丹妙药来宣传。科学家通过实验发现:如果食物中维生素 E 的含量为每毫升 5 微克,能显著延长果蝇的寿命,但是如果维生素 E 的含量增加到每毫升 25 微克,果蝇的寿命反而缩短了。其实细胞中的自由基参与了许多重要的生命活动,比如细胞增殖、细胞间通讯、细胞凋亡、免疫反应等。 由此推论不正确的是 ( )A.
自由基有其独特的作用，对机体而言是不可或缺的
B.
科学家对果蝇的实验揭示了 “ 过犹不及 ” 的道理
C.
维生素 E 的含量超过 25 微克时，会危及到人的生命
D.
. 维生素是维持人体生命的必要物质，但过量服用也会威胁生命
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