Pregnancies Can Be Dated from the Onset of the Last

Pregnancies can be dated from the onset of the last menstrual period before conception or by

A) assuming conception is two weeks after the woman's last menstrual cycle.
B) counting ahead nine months from the date the woman learned she was pregnant.
C) counting forward from the date the woman believes she conceived.
D) pregnancies are not dated as there is too much variability from woman to woman.