Delayed puberty is defined if menstruation does not occur by:

Ans. is d, i.e. 16 yearsRef: Williams gynae 3rd/ed, p329This is a controversial questionWilliams gynae 3rd/ed, p329 says"Puberty is considered delayed if no secondary sexual characteristics are noted by age 13 or if menses have not commenced by age 16"As per Medicine uptodate - delayed puberty is if mensturation does not begin by 15 years of ageBut its better to go with Williams Gynae.