In May 2010，readers who were at least 31 years old accounted for what fraction of all the readers of Magazine X?
A.fff\(\frac{1}{18}\)/fff
B.fff\(\frac{53}{250}\)/fff
C.fff\(\frac{13}{50}\)/fff
D.fff\(\frac{1}{3}\)/fff
E.fff\(\frac{7}{20}\)/fff]