I believe the answer is D. Hope this helps ;D
Answer:
genetic recombination
Explanation:
Bacteria and other harmful organisms like viruses infect people rapidly with genetic recombination.
Hope it helps.
To preserve and keep them fresh
The correct answer is frequency.
The pitch can be defined as the quality of sound produced by the rate of vibration producing it.
It is directly related to the the frequency of the sound wave. If the frequency is increased then its pitch will also increase and vice versa.
As for normal people it is a bit difficult to differentiate between the two but the musician are trained so they can differentiate the difference between the two even if the difference is 2 Hz