What type of modulation does AM radio use?

Amplitude Modulation (AM) is the correct answer because it specifically refers to the technique used in AM radio broadcasting. In amplitude modulation, the amplitude of the carrier wave is varied in proportion to the waveform of the audio signal being sent. This means that the strength of the radio signal conveys information, allowing for the transmission of voice and music over long distances.

This form of modulation is fundamental to AM radio technology, which has been in use since the early 20th century and is characterized by its ability to operate effectively in various atmospheric conditions and distances. Unlike other modulation types that might change frequency or phase, amplitude modulation stands apart by focusing solely on varying the amplitude, allowing for relatively simple transmitters and receivers for broadcasting and receiving audio content.

Other options like Analog Modulation encompass a broader category that includes multiple modulation techniques, thus not specifying the exact method used in AM radio. Active Modulation and Applied Modulation do not refer to standard terminology in the context of radio broadcasting, which makes them incorrect. Therefore, recognizing that amplitude modulation is the direct method used for AM radio clarifies why this answer stands out as the most accurate choice.