Infundibulum develops from ?
Ans. is 'c' i.e., Floor of third ventricle(Ref: Textbook of Neuroanatomy p. 112)The infundibulum of the diencephalon is a downward evagination of the floor of the third ventricle.As the infundibulum grows down, it meets an ectodermal diveiculum of the oral cavity, known as Rathke's pouch.
Floor of lateral ventricle
Floor of 4th ventricle
Floor of third ventricle
Rhombencephalon