Explanation: Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS) are the two primary methods used to implement spread spectrum technology. DSSS spreads a signal by combining the original data with a high-rate pseudorandom noise (PN) code, significantly widening the signal's bandwidth. FHSS rapidly changes the signal's carrier frequency pseudo-randomly over a wide range of frequencies. Both techniques make signals more resistant to interference, jamming, and interception by spreading the signal's energy over a wider frequency band. AM (Amplitude Modulation) and FM (Frequency Modulation) are conventional narrowband modulation types, not spread spectrum. QPSK (Quadrature Phase-Shift Keying), QAM (Quadrature Amplitude Modulation), and APSK (Amplitude and Phase-Shift Keying) are digital modulation schemes that encode data efficiently but do not inherently spread the signal's bandwidth. While they can be used *within* a spread spectrum system, they are not the *types* of spread spectrum systems themselves.