Which of these digital modes has the narrowest bandwidth?

Explanation

FT8 places eight tones 6.25 Hz apart, so the whole signal occupies only about 50 Hz. RTTY with a 170 Hz shift at 45 baud takes roughly 250 Hz, MFSK16 about 316 Hz, and PACTOR IV fills a full SSB channel of about 2.4 kHz.