Which of these digital modes does not support keyboard-to-keyboard operation?

WSPR (Weak Signal Propagation Reporter) is an automated digital mode designed purely for probing radio frequency propagation paths. It sends and receives specific, structured beacon messages (containing only a Callsign, Grid Locator, and Power level) over rigid 2-minute cycles. Because of this strict format and automated design, it is entirely unsuitable for live conversations. In contrast, RTTY, PSK31, and MFSK16 are all "ragchew" or conversational modes. They are designed for real-time "keyboard-to-keyboard" operation, where operators can type custom messages back and forth to each other just like in a live chat room. If you want to have a conversation, WSPR is the wrong tool for the job.