Recovering Fetal Cells Present in the Mother's Blood Can Be

Recovering fetal cells present in the mother's blood can be difficult because

A) only 1 in every 100,000 cells in the mother's blood is a fetal cell.
B) this technique increases the risk of miscarriage.
C) the fetal cells lack a nucleus.
D) fetal cells do not enter the mother's blood stream.
E) these cells have not been useful for diagnosing genetic disorders.