Killian's dehiscence is in: (A) Superior constrictor, (B) Inferior constrictor, (C) Middle constrictor, (D) None
Answer is B. Inferior constrictor muscle has two parts. 
Thyropharyngeus with oblique fibres and cricopharyngeus with transverse fibres.
Between these two parts exists a potential gap called "Killian's dehiscence". It is also called "Gateway of tears". 
This is also the site of herniation of pharyngeal mucosa in case of the pharyngeal pouch.