In blastula stage, trophoblast layer attach to the endometrium with the help of-
Uterine villi
Blastopore
Chorionic villi
Archenteron
In blastula stage, trophoblast layer attach to the endometrium with the help of chorionic villi. Chorionic villi is formed by the trophoblast layer and will attach to the uterine villi and complete implantation. Chorionic villi will increase surface area for absorption of nutrition.
Option c is the correct answer.