What is a blastocyst? A- a sphere of cells surrounding a hollow center B- a two celled developing structure C- A zygote covering to prevent sperm from entering D- A solid mass of about one thousand c

What is a blastocyst? A- a sphere of cells surrounding a hollow center B- a two celled developing structure C- A zygote covering to prevent sperm from entering D- A solid mass of about one thousand cella