题目

阅读理解 Can exercise during childhood protect you against memory loss many decades later?Exercise early in life seems to have lifelong benefits for the brain,in rats at least. This is an animal study,but it shows that physical activity at a young age is very important一not just for physical development,but for the whole lifelong track of cognitive（认知的）development during ageing,says Martin Wojtowicz of the University of Toronto,Canada.In humans,it may delay the appearance of Alzheimer's symptoms（阿兹海默氏症）,possibly to the point of preventing them. Wojtowicz's team d函数对任意正整数a、b满足条件，且。则 的值是（    ） A．2007        B．2008                     C．2006               D．2005