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

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