单选题 A significant reduction in caloric intake, if accompanied by vitamin supplements, will double the life span of laboratory mice. Mice fed 40 percent of the standard food allowance had twice the life expectancy of mice in a group that was fed the standard allowance.
If the information above is accurate, each of the following statements, if true, would help explain why the laboratory mice on the reduced allowance lived twice as long as the mice fed on the standard allowance EXCEPT:

A、 The lack of food reduces a mouse's metabolic rate, thereby limiting wear and tear on the mouse's body.
B、 A lower-calorie diet delays the aging of the immune system and thus protects the mouse from some diseases that usually cause death.
C、 A drastic reduction in caloric intake signals the hormonal system to delay the aging process.
D、 Mice that are fed less than the standard allowance have cells that have life spans that are longer than average.
E、 (E) The vitamin supplements that accompanied the reducedcalorie diet did not contribute calories to that diet.

【正确答案】 E

【答案解析】[解析] (E)选项是本题结论成立的前提的重述，因此(E)选项不能被用来解释老鼠饮食的改变所导致的寿命的延长，所以(E)是本题的正确答案；(A)、(B)、(C)和(D)都通过找他因的办法，从不同的例面对老鼠饮食的改变所带来的寿命的延长做了解释。