<prompt> Which one of the following is true about visualization of gestational sac?a Detected at 4 - 5 weeks by transvaginal USGb Detected at 5 - 6 weeks by transabdominal USGc Detected at 3 - 4 weeks by transabdominal USGBoth a b  <response>: All the structures are visualized at least 1 week earlier in a transvaginal USG. The positive sign that can be elicited earliest in the pregnancy is visualization of the gestational sac or fetus. With transvaginal ultrasound the gestational sac can be seen as early as 10 days after implantation. 