Which structure allows upper respiratory infections to spread from the throat to the tympanic cavity?

The Eustachian tube is the structure that allows upper respiratory infections to spread. The eustachian tube is a canal that links the middle ear to the nasopharynx, which is composed of the upper throat and the back of the nasal cavity. It also controls the pressure inside the middle ear, making it equal with the air pressure outside the body.

the atmospheric gas that forms a mild acid when dissolved in water is called carbon dioxide. the correct answer is a. 2.) chemical weathering would cause an inscription on a marble headstone to become harder and harder to read over time.