Which of the Following Statements Concerning Implantation Is Correct

Multiple Choice

Which of the following statements concerning implantation is correct?

A) Implantation is accomplished by enzymatic activity of the trophoblastic layer of the blastocyst.
B) The endometrium at the site of implantation is converted into the nutrient-rich decidua.
C) Implantation occurs within 24 hours after fertilization.
D) Both (a) and (b) above are correct.
E) All of these answers are correct.