For which range of frequencies human ears are most sensitive?
A. $2Hz{\text{ to }}3Hz$
B. $20Hz{\text{ to }}30Hz$
C. $200Hz{\text{ to }}300Hz$
D. $2000Hz{\text{ to }}3000Hz$

Hint: Frequency is the measure of how many times a repeated event occurs per unit time. Frequency of a sound means the number of vibrations counted per second.
Normal human ears are able to detect sounds in a frequency range from about $20Hz{\text{ to 20000}}Hz$. But our hearing is most sensitive in higher regions.

Complete step by step answer:
Let's first discuss the frequency of sound waves.
Frequency is the measure of how many times a repeated event occurs per unit time. Frequency of a sound means the number of vibrations counted per second.
Normal human ears are able to detect sounds in a frequency range from about $20Hz{\text{ to 20000}}Hz$. But our hearing is most sensitive in higher regions, mostly $2000Hz{\text{ to }}3000Hz$.
A human child can actually detect sound frequencies slightly higher than 20 kHz, but lose some high-frequency sensitivity as they grow; the upper limit in average adults is mostly close to 15–17 kHz.
Hence, the correct option is D.

Note: Most of the small mammals are sensitive to very high frequencies, but not to the lower frequencies. For example, some species of bats can detect sound of frequency as high as 200 kHz, but their lower limit is around 20 kHz which is the upper limit for young humans having normal hearing. Similarly, only dogs can hear the sound of a dog whistle but we can’t because the dog whistle produces a sound of much higher frequency that humans can’t hear but dogs can hear as their frequency is much higher than that of humans.