This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
A midline cleft lip is present when there is failure of fusion between the following structure: 
Select and explain. 
A. Mandibular processes, B. Medial nasal processes, C. Medial and lateral nasal process, D. Medial nasal and maxillary process.
B: Medial nasal processes
Answer: B: Medial nasal processes 
Explanation: Clefting of the lip and/or palate is felt to occur around the eighth week of embryogenesis, either by failure of fusion of the medial nasal process and the maxillary prominence or by failure of mesodermal migration and penetration between the epithelial bilayer of the face. The cause of orofacial clefting is felt to be multifactorial. Factors that likely increase the incidence of clefting include,Increased parental ageDrug useInfections during pregnancySmoking during pregnancyFamily history of orofacial cleftingRef: Losee J.E., Gimbel M., Rubin J., Wallace C.G., Wei F. (2010). Chapter 45. Plastic and Reconstructive Surgery. In F.C. Brunicardi, D.K. Andersen, T.R. Billiar, D.L. Dunn, J.G. Hunter, J.B. Matthews, R.E. Pollock (Eds), Schwaz's Principles of Surgery, 9e.