Sonar is a device that uses reflected sound waves to measure underwater depths.

the frequency of the signal is

b)254hz

The appropriate answer is a. they are not closely packed. Molecules in a gas are not closely packed but a scattered in a rather disorderly fashion. Atoms packed or arranged in an orderly pattern are solids. Helium atoms would not have an attraction to each other because helium is an inert gas. Inert gases are nonreactive.