Question

fill in the blank question
when the early developing embryo consists of a hollow ball of cells with an inner cell mass, it is referred to as a

Explanation:

In human embryonic development, after cleavage and morula stage, the embryo forms a blastocyst. A blastocyst is a hollow ball of cells (trophoblast cells forming the outer layer) with an inner cell mass (which will develop into the embryo proper). This is a key stage in early embryonic development.

Answer:

blastocyst