This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Embryology, Subject name: Anatomy
Which of the following is the derivative of ultimobranchial body? 
Select and explain. 
A. Thyroid, B. Parafollicular 'C' cells, C. Capsule of thyroid, D. 2nd branchial pouch
B: Parafollicular 'C' cells
Answer: B: Parafollicular 'C' cells 
Explanation: Ans. B Parafollicular 'C' cellsRef: Gray's Anatomy E-book. P 61ENDODERMAL POUCHES* 1st pouch: Dorsal part forms tub tympanic recess which forms the middle ear cavity and eustachian tube.* 2nd pouch: Joins with ventral part of 1st pouch to form palatine tonsil. Also forms parts of middle ear.* 3rd pouch: Dorsal part forms the inferior parathyroid gland and ventral forms thymus.* 4th pouch: Dorsal part forms the superior parathyroid gland.# Ventral part forms the ultimobranchial body which forms the parafollicular C-cells of thyroid.