Question

multiple cholce question
implantation occurs when:
the inner cell mass is formed
the blastocyst attaches to the uterine wall
the sperm penetrates the egg
the trophoblast is formed

Explanation:

Implantation is a key process in embryonic development. The blastocyst is the stage of the embryo that implants. When the blastocyst attaches to the uterine wall, this is defined as implantation. The inner cell mass forms part of the blastocyst but its formation is not implantation. Sperm penetrating the egg is fertilization. The trophoblast is a layer of cells in the blastocyst, but its formation alone is not implantation.

Answer:

the blastocyst attaches to the uterine wall