Gynaecology & Obstetrics General 30934853 Ovulation is presumed to have occurred if progesterone level is __________ on day 21 A 0.3 ng / mL B 3 ng / mL C 30 ng / mL D 300ng / mL High-Yield Explanation Ovulation can be safely assumed to have occurred if progesterone level exceeds 3 ng / mL on cycle day 21.