At the time of implantation, the human embryo is in a stage of development known as the ________.

A) fetus
B) zygote
C) morula
D) blastocyst
E) ovum

Implantation

Attachment of the blastocyst to the endometrium of the uterus, occurring 6 or 7 days after fertilization of the ovum.

Human Embryo

An early developmental stage of human growth and differentiation, starting from fertilization to the eighth week, where major organs and structures begin to form.

Blastocyst

Stage of mammalian embryos that consists of the inner cell mass and a thin trophoblast layer enclosing the blastocele.