What element of nature are typical in the use of the siren

Air

Explanation:

A siren is a device that produces sound waves due to the flow of air through a series of holes. It consists of a rotating disk which has series of holes drilled at required distances to one another, and a nozzle through which air flows.

The nozzle is arranged in such a way that it forces air through the holes of the rotating disk, thus producing sound with appropriate frequency.

Sirens are used for security purpose, in ambulances etc.

ich statement best shows a problem in travels with charley?

one sharp difficulty presented itself. in the intervening twenty-five years my name had become reasonably well known.

this being so, my trip demanded that i leave my name and my identity at home.

i had to go alone and i had to be self-contained, a kind of casual turtle carrying his house on his back.

with all this in mind i wrote to the head office of a great corporation which manufactures trucks.

easy - boys have problems.

i hope this ! (: