What Is the First Event in the Development of the Face

Multiple Choice

What is the first event in the development of the face during the later part of the fourth week of prenatal development?

A) Disintegration of the oropharyngeal membrane
B) Paired mandibular processes fusion at the midline to form the mandibular arch
C) Folding of the embryonic structure into a tubal one
D) Thickening of the facial placodes