In amplitude modulation,

In amplitude modulation, the modulation index m, is kept less than or equal to 1 because

(a) m > 1, will result in interference between the carrier frequency and message frequency, resulting in distortion

(b) m > 1 will result in overlapping of both sidebands resulting into loss of information

(c) m > 1 will result in a change in phase between the carrier signal and the message signal

(d) m > 1 indicates the amplitude of message signal greater than the amplitude of the carrier signal resulting in distortion