This is a Multiple Choice Questions as classified in NCERT Exemplar
Answer- a, b, c
Explanation- production of modulated wave is given by frequency of upper side band – frequency of lower side band so in first three cases it is clearly visible.
µ = A? /A? = 0.5 {A? = 20 volt, A? = 40 volt} m (t) = A? sin ω? t {ω? = 2π×10? } c (t) = A? sin ω? t {ω? = 2π×10×10³} C? (t) = (A? + A? sin ω? t) sin ω? t ⇒ A? {1+ µsin ω? t} sin ω? t