What is the signal transmitted in J2B mode?

Correct Answer: Option C — An upper sideband of 2 alternating tones.

J2B is the emission designation for digital data transmission using single sideband with a suppressed carrier. It utilizes two distinct audio tones, representing mark and space, which are modulated onto the upper sideband. This is commonly used for NBDP (Narrow Band Direct Printing) telex communications in maritime radio.