Correct Answer - A
For transmitting a signal, we need an antenna or an serial. Thus antenna should hav e a size comparable to the wavelength of the signal to the signal. For an electromagentic wave of freqeuncy 20 kHz. The wavelength is 15km. Obviously such a long antenna is not possible to constract and operate Hence direct transmission of such baseband signal is not p ractical. Therefore there is a need of translating the information contained in our original low frequency baseband signal into high or radio frequencies before transmission.
