The Difference(s) Between the Maxillary and Mandibular Central Incisors Is(are)

The difference(s) between the maxillary and mandibular central incisors is(are) the:

A) maxillary central incisors are larger than the mandibular central incisors in all dimensions.
B) labial surfaces of the maxillary central incisors are more rounded from the incisal aspect than those of the mandibular central incisors.
C) cingulum in less prominent on the maxillary central incisors than the cingulum on the mandibular central incisors.
D) both a and b.