8 year-old child had fractured his maxillary central incisor
10-months ago. The pulp shows no response. There is no periapical lesion in the radiograph. The treatment of choice is:
(A) Ca(OH)2 pulp capping (B) Formocresol pulpotomy (C) Conventional root canal treatment (D) Complete debridement and apexification
(D) Apexification 
Definition
“Apexification is defined as chemically induced root formation by calcium hydroxide or CMCP in nonvital immature, blunderbuss canals of young permanent teeth.”
APEXIFICATION 
It is a method of inducing apical closure by formation of mineralized tissue in the apical region of a nonvital permanent tooth with an incompletely formed root apex. 
It is defined as a method to induce development of the root apex of an immature pulpless tooth by formation of osteocementum/bone-like tissue (Cohen). 
Apexification is a method of inducing apical closure through the formation of mineralized tissue in the apical pulp region of a nonvital tooth with an incompletely formed root and an open apex (Morse et al. 1990).