Correct Answer - Option 3 : Carson's rule
Explanation:
Carson's rule states that the bandwidth required to transmit an angle modulated wave is twice the sum of the peak frequency deviation and highest modulating signal frequency.
According to Carson rule signal, BW is given as:
B.W = (β + 1) 2fm
\(\becauseβ=\frac{Δf}{f_m} \)
B.W. = 2[Δf + fm]
If multiple frequencies are available in modulating signal then,
B.W. = 2(β + 1) fmax