Question

the pre - embryonic structure that enters the uterus is a fluid - filled ball of cells with an inner cell mass called a __________.a blastocystb trophoblastc morulad zygote

Explanation:

• A blastocyst is a pre - embryonic structure that is a fluid - filled ball of cells with an inner cell mass.
• The trophoblast is a part of the blastocyst that forms the outer layer and is involved in implantation, not the whole structure described.
• A morula is a solid ball of cells (16 - cell stage) before the blastocyst stage.
• A zygote is the single - celled fertilized egg.

Answer:

A. blastocyst