E2E03:To what does the "4" in FT4 refer?
Direct answer summary (2024-2028 NCVEC pool)
The official correct answer for E2E03 is Four-tone continuous-phase frequency shift keying.
The key fact is Four-tone continuous-phase frequency shift keying. Match that fact to the exact condition in the question; the other choices describe a different rule, band, component, or operating situation.