Answer:
c) 7-8 days after implantation
Explanation:
hCG or Human Chorionic Gonadotropin is used as a marker in pregnancy test kits. It is produced by the trophoblastic cells once the embryo has been implanted in the uterus. It becomes detectable in urine usually a week after implantation. Its level increases at the beginning of pregnancy up till 8-11 weeks and then falls off and becomes constant.