Which of the following narrow-band digital modes can receive signals with very low signal-to-noise ratios?

FT8 is a highly popular digital mode designed specifically by Joe Taylor (K1JT) and Steve Franke (K9AN) for weak-signal communication. It utilizes advanced forward error correction (FEC) and precise time synchronization, allowing it to decode signals that are buried deep in the noise floor, often well below human hearing capability. While modes like MSK144 are used for meteor scatter (which relies on quick bursts), and AMTOR or MFSK32 are older digital modes, FT8 excels at extreme low signal-to-noise ratios (SNR). It can routinely decode signals at -20 dB or even -24 dB SNR in a standard 2.5 kHz bandwidth.