Ans. is d i.e. 14 days after ovulation The first definitive sonographic finding to suggest early pregnancy is visualization of the gestational sac. Using transvaginal transducers with frequency of 5 MHz, the size threshold for sac detection is 2 - 3 mm, corresponding to 4 weeks + 1 day gestational age to 4 weeks + 3 days gestational age." To understand how many days after ovulation, you should first understand that gestational age is calculated from 1st day of last menstrual period. As is evident from above diagram gestational sac is visualised approximately 15-17 days after ovulation (or within 1-3 days of missed period) but since it is not given in options so the nearest possible answer is 14 days after ovulation.