Answer:

Introduction:
The pitch of sound refers to how high or low a sound is perceived by the human ear. It is determined by the frequency of the sound wave. The pitch of sound is an important characteristic that helps us differentiate between different sounds.

Explanation:
The correct answer to this question is option 'A' which states that the pitch of sound depends on frequency. Let's understand why frequency is the determining factor for the pitch of sound.

1. Frequency:
- Frequency refers to the number of vibrations or cycles per second. It is measured in Hertz (Hz).
- Higher frequency sound waves have more cycles per second, which results in a higher pitch.
- Lower frequency sound waves have fewer cycles per second, which results in a lower pitch.
- For example, a high-pitched sound like a whistle has a higher frequency, while a low-pitched sound like a bass drum has a lower frequency.

2. Relation to Pitch:
- Our ears perceive higher frequency sound waves as having a higher pitch and lower frequency sound waves as having a lower pitch.
- This is because the sensory cells in our ears, known as hair cells, are sensitive to different frequencies of sound.
- When high-frequency sound waves enter our ears, they stimulate the hair cells that are tuned to high frequencies, and our brain interprets this as a high-pitched sound.
- Similarly, when low-frequency sound waves enter our ears, they stimulate the hair cells that are tuned to low frequencies, and our brain interprets this as a low-pitched sound.

Conclusion:
In conclusion, the pitch of sound is determined by the frequency of the sound wave. Higher frequency sound waves result in a higher pitch, while lower frequency sound waves result in a lower pitch. Understanding the relationship between frequency and pitch helps us differentiate between different sounds and appreciate the diversity of the auditory world around us.