Which range is listed as the audio signal range in the material?

• A. 3 Hz - 30 Hz
• B. 3 kHz - 30 kHz
• C. 30 Hz - 300 Hz
• D. 300 Hz - 3 kHz

Answer: (A)

The key idea here is to know what the material uses as the band for audio signals. In this material, the audio signal range is defined as 3 Hz to 30 Hz. That means the content you’re studying specifies audio information occupying that very low-frequency band, well below typical human hearing. The other ranges fall outside what the material designates as the audio signal range: 3 kHz to 30 kHz is outside the audio band in this context and is more like a high-frequency or RF range; 30 Hz to 300 Hz and 300 Hz to 3 kHz lie within the audible spectrum but do not match the material’s stated low-frequency range. So 3 Hz to 30 Hz is the best choice because it aligns exactly with how the material defines “audio signal range.”