题目

    People born in the autumn live longer than those born in the spring and are less likely to fall chronically ill when they are older, according to an Austrian scientist. Using census data for more than one million people in Austria, Denmark and Australia, scientists at the Max Planck Institute for Demographic Research in the northern German town of Rostock found the month of birth was related to life expectancy over the age of 50. Seasonal differences in what mothers ate during pregnancy, and infections occurring at different times of the year could both have an impact on the health of 设φ∈R，则“φ=0”是“f（x）=cos（x+φ）（x∈R）为偶函数”的（　　）A．充分而不必要条件B．必要而不充分条件C．充分必要条件D．既不充分也不必要条件