Final answer:
After a secondary oocyte is fertilized, it secretes d) Human chorionic gonadotropin (hCG) to maintain the corpus luteum and support the developing pregnancy, and this can be detected through a urine pregnancy test within days of implantation.
Step-by-step explanation:
If a secondary oocyte is fertilized and successfully implants in the uterine lining, it becomes a pre-embryo and begins to secrete option d)Human chorionic gonadotropin (hCG).
This hormone is secreted by the trophoblast cells of the blastocyst and is crucial for maintaining the corpus luteum. The corpus luteum can continue to secrete progesterone and estrogen, necessary to maintain the pregnancy and prevent menses. The hCG hormone is so vital that within a few days of implantation, it can be detected in a urine pregnancy test.