Implantation occurs 6-10 days after ovulation

Steps:

• Menstruation begins on day 1; follicular phase builds up to ovulation around day 14.
• Ovulation releases the egg; fertilization happens within 24 hours if sperm is present.
• The fertilized egg travels to the uterus, implanting 6-10 days post-ovulation (around days 20-24).
• Diagram labels correspond to cycle days; D marks this post-ovulatory window.

Why D is correct:

• Implantation aligns with the secretory phase when the endometrium is receptive, 6-10 days after ovulation per reproductive physiology.

Why the others are wrong:

• A: Occurs during menstruation (days 1-5), when the endometrium sheds, preventing implantation.
• B: Falls in the follicular phase (pre-ovulation), before egg release and fertilization.
• C: Aligns with ovulation (around day 14), too early for the embryo to reach the uterus.

Final answer: D