2.) a radio wave in a vacuum has a wavelength
of 0.045 m. what is its frequency?
sound, em, other

Frequency = 667 MHz.

EM

Explanation:

The radio waves are the electromagnetic waves of a particular range of frequencies.

Unlike the sound waves which require a medium to propagate, the radio waves can travel in a vacuum.

The frequency of the radio waves ranges between 300 MHz to 600 MHz.

The relation between the frequency and wavelength is given by the relation

                                f = c / λ      Hz

Where c is the velocity of electromagnetic waves. c = 3 x 10⁸ m/s

Given that the wavelength, λ = 0.045 m

Substituting in the above equation

                                 f = 3 x 10⁸ m/s  / 0.045 m

                                   = 667 MHz

Hence, the frequency of the radio waves is, f = 667 MHz

It is electromagnetic radiation (EM).

there is no correct list among the choices you've provided.

the list might look something like this:

-- baby human

-- piccolo

-- flute

-- soprano singer

-- trumpet

-- tenor singer

-- trombone

-- baritone singer

-- baritone horn

-- bass singer

-- tuba

since i had to make up the list myself, i made it easy on myself, and i didn't try to shuffle the string instruments and woodwinds into it too.

a.   mass number from atomic number