Study the graph given below.

From the options given below, select the time period during which corpus luteum exists in the ovary?

Corpus luteum is formed after the ovulation. In the given graph, ovulation occurs on 14th day. So the corpus luteum formed from the remnant of Graafian follicle after the release of ovum exists from about 14th to 25th day. It persists if the fertilisation occurs. It degenerates to whitish scar in case fertilisation does not occur, leading to menstruation around 28th day. Of the given options, answer is 20th day.