Progesterone rises post-ovulation in the luteal phase

Steps:

• Identify menstrual cycle phases: follicular (days 1-14) and luteal (days 15-28).
• Note ovulation at mid-cycle (~day 14), after which corpus luteum forms.
• Recall progesterone secretion by corpus luteum causes levels to rise sharply in luteal phase.
• Match graph line: select the one low in follicular phase, peaking mid-luteal, then declining.

Why C is correct:

• Line C rises after mid-cycle ovulation and peaks in luteal phase, matching progesterone's role in maintaining uterine lining per endocrine physiology.

Why the others are wrong:

• A: Peaks early follicular phase, characteristic of FSH surge.
• B: Sharp mid-cycle spike, typical of LH ovulation trigger.
• D: Gradual follicular rise with pre-ovulation peak, aligns with estrogen pattern.

Final answer: C