3. if you send a sound wave of the same wavelength (λ = 2.00 m) through air, helium, and carbon dioxide, describe how the pitch of the sound will compare through each medium. use calculations and your data to explain

The speed of sound is in the gas is given with this formula:

Where T is the temperature, M is the molar mass of the gas, R is universal gas constant and is heat capacity ratio.
We can find the speed of the sound in different gasses online ( you could also calculate it using above formula). 

We know that pitch, wavelength, and speed of the sound are related:

Because our wavelentgh is the same the frequency must be different.

Your answer is c. explanation: plasma  is the fourth state of matter, derived from the gaseous state of matter.  plasma  can contain free  electrons  and/or  ions. while  plasma is never neutral, it can either be positively or negatively charged.  gases, however, are electrically neutral.