Which of These Would a Paleontologist Be Most Likely to Do

Which of these would a paleontologist be most likely to do in order to determine whether a fossil represents a reptile or a mammal?

A) Look for the presence of milk-producing glands.
B) Look for the mammalian characteristics of a four-chambered heart and a diaphragm.
C) Because mammals are eutherians,look for evidence of a placenta.
D) Use molecular analysis to look for the protein keratin.
E) Examine the teeth to determine how sharp or ground down they are.