Question

Lungs possess a very large number of tiny microscopic sacs. A lubricant
prevents their collapse. The wall of these sacs is one cell thick. It is n close
contact with a network of blood capillaries. Lung sacs receive fresh air with each
Inhalation. Blood capillaries contain deoxygenated blood rich in carbon dioxide.
The sacs create very large surface area, many times the surface area of the body.
1) The collapsing of trachea, bronchi and bronchioles is prevented by:
a) Attachment to bony cover
b) Presence of cartilage rings
c) Occurrence of thick strong walls
d) Occurrence of dense connective tissue on the inner side​

Answer 1

Answer:

b presence of cartilage rings strictly speaking incomplete cartilage rings