Correct Option: C

The basic principle of Armstrong (Indirect) method is to generate a narrowband FM (NBFM) indirectely by using the phase-modulation technique, and then converting this NBFM to a wideband FM (WBFM). The Armstrong FM transmitter performs frequency multiplication in stages to find the desired value of carrier frequency as well as the frequency deviation, since the desired multiplication factors for carrier frequency and frequency deviation are not the same. If the multiplication is done in one shot, the carrier frequency as well as the deviation is multiplied by the same factor which is not desired. Hence multiplication is done in stages.