A standard menstrual cycle lasts $28$ days, and day $1$ marks the beginning of menstruation. On which day is the lining of the uterus at its thickest?
- A$1$
- B$4$
- C$9$
- D$21$
Biology 0610 · IGCSE · Sex hormones in humans
A standard menstrual cycle lasts $28$ days, and day $1$ marks the beginning of menstruation. On which day is the lining of the uterus at its thickest?