Which of the following statements about the human respiratory system are INCORRECT ?
I. During swallowing , glottis can covered by a thin elastic cartilaginous flap called epiglottis to prevent the entry of food into the larynx.
II. The trachea is a straight tube extending up to the mid- thoracic cavity, which divides at the level of the fourth thoracic vertebra into a right and left primary bronchi.
III. The trachea , primary secondary and tertiary bronchi, and initial bronchioles are supported by incomplete cartilaginous rings made up of hyaline cartilage.
IV. The respiratory part transports the atmospheric air to the alveoli, clear it from foreign particles, humidifies and also brings the air to body temperature.