AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
Menstruation occurs every month because the ovary releases one egg every month, and the uterus prepares itself by thickening its lining with blood and mucous to nourish a possible embryo. If the egg is not fertilised, this lining is no longer needed, so it breaks down and comes out through the vagina as blood and mucous — a process called menstruation.
Source: Chapter 7, Section 7.3.3(c)
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The examiner expects two linked points: (1) the monthly release of an egg causes the uterine lining to thicken, and (2) when fertilisation does not occur, that lining sheds as menstruation. Always mention both the cause (unfertilised egg) and the effect (shedding of uterine lining) to secure both marks.