The correct option is A 0.05s to 5×10−5 s
The frequency (f) of a wave is the number of full waveforms generated per second. This is the same as the number of repetitions per second or the number of oscillations per second.
Time Period (T) is the number of seconds per waveform or the number of seconds per oscillation. It is clear that frequency and period are reciprocals.
In this case, the Frequency range of audible sound for humans is 20Hz and 20000Hz.
Time period for 20 Hz = 1f=120=0.05s
Time period for 20,000 Hz = 1f=120000=5×10−5s.
Hence, the time period range is 0.05s to 5×10−5s.