This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharynx, larynx and trachea and cranial nerves 3,4,6, Subject name: Anatomy
All are true regarding trachea EXCEPT? 
Select and explain. 
A. Has C shaped cailages, B. Outer diameter is 2 cm, C. More than 20 hyaline cailages, D. Isthmus of thyroid gland lies at 2, 3 and 4th tracheal rings
C: More than 20 hyaline cailages
Answer: C: More than 20 hyaline cailages 
Explanation: Trachea Length - 10- 15cm Diameter - 2cm (males), 1.5cm (females) Upper end - at lower end of cricoid cailage. Lower end - sternal angle C6 - T6 (erect position in living person). Fibroelastic wall. Cailaginous skeleton suppoed by 16 - 20 C- Shaped rings. Lumen lined by ciliated pseudostratified columnar epithelium