In the context of the Physical Layer, how is data typically converted for transmission over a medium?

Question $1$ options:

Data is encrypted into cipher text regardless of whether the transmission medium is analog or digital.

Data is converted into analog signals for transmission over analog channels and into digital signals for digital channels.

Data is broken down into packets but remains in digital form for both analog and digital transmission channels.

Data is converted into analog signals for transmission over digital channels and into digital signals for analog channels.