Which of the following is a form of amplitude modulation?

Single sideband (SSB) is an extremely popular and efficient form of amplitude modulation (AM). A standard AM transmission consists of a central carrier wave and two identical sidebands (upper and lower) that contain the voice information. In an SSB transmitter, the carrier wave and one of the sidebands are suppressed before transmission. Because the remaining sideband is essentially just a sliced portion of a standard AM signal, it is still classified as a form of amplitude modulation. Distractors like Phase Shift Keying (PSK) and Spread Spectrum use phase modulation or digital techniques, not amplitude variations, to encode information.