Which of the following emission modes requires that an amateur radio station have means to prevent or indicate overmodulation?

Overmodulation in amplitude-based voice modes like Single Sideband (SSB) causes excessive bandwidth and splatter, which can severely interfere with adjacent frequencies. Canadian regulations require stations using these modes to have a way to monitor or prevent this overmodulation. Frequency Modulation (FM) uses frequency deviation, not amplitude modulation, so it is limited by deviation circuits rather than modulation amplitude limits. RTTY and CW are digital and continuous wave modes where voice-style overmodulation does not apply. To comply with the rules, modern transceivers use Automatic Level Control (ALC) circuits to prevent SSB overmodulation, and operators monitor their ALC meters to ensure proper audio drive levels.