Question

Question #9efb6

Answer 1

Anterior and lateral walls.

Explanation:

Trachea also known as wind pipe is a respiratory tube that contains `15-20` `"C-shaped"` rings made up of hyaline cartilage. These rings cover the trachea on it's lateral sides & anterior portion while the posterior one being faced by oesophagus or food pipe has no `"C-shaped"` rings. Because posteriorly these are replaced by fibroblast connective tissues called annular ligaments.

The basic purpose of these rings is to keep the tracheal tube taut during exhalation or inhalation. These cartilaginous rings prevents the trachea form over-expanding and from collapsing. Hence help it to perform it's function efficiently.
And the fibroblast elastic tissues joining these cartilages are helpful to esophagus as they push the trachea slightly inward for the convenient passage of food from the food pipe.

Hope it helps...