When the modulating frequency is doubled, the modulation index is halved, and the modulating voltage remains constant. The modulation system is1. Amplitude modulation2. Phase modulation3. Frequency modulationSelect the correct answer from the codes given below:

When the modulating frequency is doubled, the modulation index is halv

1.	When the modulating frequency is doubled, the modulation index is halved, and the modulating voltage remains constant. The modulation system is1. Amplitude modulation2. Phase modulation3. Frequency modulationSelect the correct answer from the codes given below:
A.	1 only
B.	2 only
C.	3 only
D.	1, 2 and 3
Answer» D. 1, 2 and 3