Question

what is a blastocyst?
a type of bacteria found in the human gut
a cluster of cells that forms after fertilization and eventually implants in the uterine lining
a cyst containing puss
a type of white blood cell
a cyst containing fluid

Explanation:

A blastocyst is an early - stage embryo that forms after fertilization. It is a cluster of cells. The other options are incorrect: bacteria in the gut are microorganisms unrelated to embryonic development; a cyst with pus is an infected cyst; a white blood cell is part of the immune system; and a fluid - containing cyst is a general cyst description not specific to embryonic development.

Answer:

A cluster of cells that forms after fertilization and eventually implants in the uterine lining.