Corpus leuteum stas regressing after how many days of ovulation ?

Ans. is 'b' i.e., 10 daysIf ovum is not feilized, the corpus luteum stas degenerating around day 24 of cycle (about 10 days after ovulation) and is eventually is replaced by fibrous tissue, forming corpus albicans.Degeneration of corpus luteum is due to decline in level of LH (which is required for maintenance of corpus luteum) and increase in secretion of inhibin by luteal cell itself.