Which of the Following Fetal Attitudes Is the Most Advantageous

Which of the following fetal attitudes is the most advantageous for birth?

A) The spine is bowed forward; the head is flexed with the chin touching the sternum; the arms and legs are flexed and folded on the chest; thighs are flexed into the abdomen; calves are pressed against the back of the thighs.
B) The chin is not touching the chest; occipital frontal diameter is the presenting part.
C) The brow of the head is the presenting part; fetus is in partial extension.
D) The back is arched; the neck is extended; occipitomental diameter of the head is the presenting part; fetus is in full extension.