The correct choice is
D. 22 Hz and 42 Hz.
In fact, the beat frequency is given by the difference between the frequencies of the two waves:
In this problem, the beat frequency is 
, therefore the only pair of frequencies that gives a difference equal to 20 Hz is
D. 22 Hz and 42 Hz.
<span>to preserve foods, dye fabric, and DE-ice roads i hopes this helps
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It is helpful to study the light that comes off stars because C. The light from a star gives hints of what elements make up a star.
Answer:
Acidity
Explanation:
pH measures how acidic or basic a substance is.
