Answer:
A. All of the cells of a developing fetus
Explanation:
As stated in the question, the blastocyst is a collection of cells formed as a result of several divisions of the ZYGOTE. This means that the zygote at some point becomes a blastocyst. The blastocyst itself is a collection of cells that make up the inner and outer layer. The outer layer is called trophectoderm, which gives rise to the trophoblast that later develops into the PLACENTA that nourishes the embryo.
The cells that make up the inner layer forms the embryo. These cells are stem cells that will eventually differentiate into all the cell types that makes up an embryo.
