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Conclusion
¥A.  one-to-one correspondence exists between the representation of a given signal in the time domain and in the frequency domain.
¥B. The character of the power spectrum allows us to determine if a signal is aperiodic or periodic in the time domain.  A periodic signal has a discrete frequency spectrum while an aperiodic signal has a continuous spectrum.
¥C. The amplitude spectrum and phase spectrum together allow us to reconstruct the signal in the time domain.  If only the amplitude spectrum or power spectrum is available, it is possible to make some conclusions about features of the signal in the time domain.
¥D. The presence of a DC offset means that the signal has a constant component, and the entire signal is shifted along the voltage axis in the time domain. 
¥I.  If all harmonics divisible by a number n are  missing for a rectangular periodic signal, the rectangular signal in the time domain has a duty cycle d equal to 1/n .
¥F. The power spectrum allows us to determine the full bandwidth and the effective bandwidth of the signal.
¥G. Bandwidth refers to the range of frequencies represented in an analog signal.  The bandwidth of an analog signal determines the maximum sampling rate for a digital signal that is accurately transmitted via this analog signal.