39. All of the following statements are true regarding fontanelles except
a. The sphenoid, mastoid, and posterior fontanelles close after two
months, while the anterior fontanelle may exist for up to two years.
b. They allow the skull to enlarge to accommodate the growing brain.
c. The sphenoid, mastoid, posterior, and anterior fontanelles are
present in infants up to the age of two years.
d. They are large fibrous membranes between the cranial bones in
fetuses and newborns.