Which mode of radio transmission is more susceptible to interference?

Amplitude modulation (AM) is considered more susceptible to interference compared to other modes of radio transmission. This stems from the fundamental way AM works—by varying the amplitude, or strength, of the carrier wave to encode information. Ambient noise and other electromagnetic interferences, such as lightning or electronic devices, can easily alter the amplitude of the wave. When such interference occurs, it directly affects the quality of the received signal, potentially distorting the information being transmitted.

In contrast, frequency modulation (FM), digital modulation, and phase modulation have mechanisms that allow them to maintain signal integrity better in the presence of noise. For example, FM encodes information in the frequency variations of the carrier wave rather than amplitude, which gives it inherent resistance to amplitude-based interference. Digital and phase modulation techniques also utilize methods that minimize the effects of received noise, enhancing their performance in various conditions. Thus, AM's reliance on amplitude makes it particularly vulnerable, highlighting why it is the correct answer in this context.