Confucius’s sentence “ When one is fifty, one may read the Book of Changes.” suggests that _______.
选项：

A: only when one is mature enough, can he appreciate the wisdom in the Book of Changes ;
B:the age of fifty is a proper age to read the Book of Changes ;
C:when one is fifty, one should read the Book of Changes;
D:only when one is fifty, can he have interest in the Book of Changes