The largest fontanel is the ________ fontanel.

A) sphenoidal
B) mastoid
C) ethmoid
D) anterior
E) posterior

The largest fontanel is the anterior fontanel, which is located at the junction of the sagittal and coronal sutures. It typically measures about 2-3 cm in diameter and can remain open up to 18-24 months after birth. The other fontanels listed are smaller in size and located in different parts of the skull.