B is the answer that I know of.
For the majority of instruments f = n f0 where f is the resonating frequency, n is any whole number and f0 is the fundamental.
<span>This applies to trumpets, violins, flutes and a broad range. </span>
<span>In such a </span>case<span> the first harmonic would be at n=1 and the second harmonic would be at n=2 </span>
<span>which gives a frequency of 84 Hz</span>
According to funtriva.com, the piece that allows you to adjust the amount of light that's coming through the microscope is called the adjustable diaphragm. It is located under to stage (where what you are observing is placed on) and can be rotated to make the light<span> intensity change</span>